Helaman 13:5

And he said unto them: Behold, I, Samuel, a Lamanite, do speak the words of the Lord which he doth put into my heart; and behold he hath put it into my heart to say unto this people that the sword of justice hangeth over this people; and four hundred years pass not away save the sword of justice falleth upon this people.

This is not exactly a prophecy of imminent destruction. Four hundred years is a long time. Unbelievers in Samuel's day scoffed at such a prophecy because it was impossible to substantiate. Yet the patience of history proved him right. The prophecies of the Second Coming do not include a specific time frame, nevertheless, we are told that the day fast approaches. It may seem to us to be as remote as Samuel's prophecy. But the prophesied day of destruction came for the Nephites, and the Second Coming will arrive one day for us or our posterity. We do not have the luxury of a fixed timetable, so we dare not procrastinate our preparation

Helaman 13:3

But behold, the voice of the Lord came unto him, that he should return again, and prophesy unto the people whatsoever things should come into his heart.

The Lord did not tell Samuel ahead of time what message he was to take to the people of Zarahemla. I'm sure Samuel had a pretty good idea, but he did not know exactly what to say when he started. He had to open his mouth in faith, and then the words came. Nephi was likewise tested when he was told to return to Jerusalem to get the brass plates, not knowing beforehand what he should do. We may be tested in the same way. We may get a prompting from the Holy Spirit without seeing the whole picture. We have to act without knowing the outcome. To one such as I who analyzes everything and plans meticulously, acting on faith is a particularly challenging test. Only when faith is stronger than fear do we receive the help and answers we need. Act first, and then come the miracles.

Helaman 12:8-23

For behold, the dust of the earth moveth hither and thither, to the dividing asunder, at the command of our great and everlasting God. Yea, behold at his voice do the hills and the mountains tremble and quake. And by the power of his voice they are broken up, and become smooth, yea, even like unto a valley. Yea, by the power of his voice doth the whole earth shake; Yea, by the power of his voice, do the foundations rock, even to the very center. Yea, and if he say unto the earth—Move—it is moved. Yea, if he say unto the earth—Thou shalt go back, that it lengthen out the day for many hours—it is done; And thus, according to his word the earth goeth back, and it appeareth unto man that the sun standeth still; yea, and behold, this is so; for surely it is the earth that moveth and not the sun. And behold, also, if he say unto the waters of the great deep—Be thou dried up—it is done. Behold, if he say unto this mountain—Be thou raised up, and come over and fall upon that city, that it be buried up—behold it is done. And behold, if a man hide up a treasure in the earth, and the Lord shall say—Let it be accursed, because of the iniquity of him who hath hid it up—behold, it shall be accursed. And if the Lord shall say—Be thou accursed, that no man shall find thee from this time henceforth and forever—behold, no man getteth it henceforth and forever. And behold, if the Lord shall say unto a man—Because of thine iniquities, thou shalt be accursed forever—it shall be done. And if the Lord shall say—Because of thine iniquities thou shalt be cut off from my presence—he will cause that it shall be so. And wo unto him to whom he shall say this, for it shall be unto him that will do iniquity, and he cannot be saved; therefore, for this cause, that men might be saved, hath repentance been declared. Therefore, blessed are they who will repent and hearken unto the voice of the Lord their God; for these are they that shall be saved.

God has power over all physical creation and all the elements. Man also has limited power over physical elements,  but man's power is different from God's. Man's power depends on force and coercion.  Man can move a mountain,  but it takes time, physical exertion, tools, machinery, and explosives. God moves the mountain by his word alone. His voice is sufficient. He speaks his will and the elements obey. They move of their own accord without coercion or compulsion. Whatever man can do, God can do better, bigger, faster, easier, and he has done it first.

At the end of this long list of powers is the one power that man cannot emulate or usurp.  That is God's power to save us. God may delegate many powers to man through the priesthood, including the power to seal up into eternal life, but only God can grant eternal life. Only he can save our immortal souls through the atonement of Jesus Christ.

Helaman 12:2

Yea, and we may see at the very time when he doth prosper his people, yea, in the increase of their fields, their flocks and their herds, and in gold, and in silver, and in all manner of precious things of every kind and art; sparing their lives, and delivering them out of the hands of their enemies; softening the hearts of their enemies that they should not declare wars against them; yea, and in fine, doing all things for the welfare and happiness of his people; yea, then is the time that they do harden their hearts, and do forget the Lord their God, and do trample under their feet the Holy One—yea, and this because of their ease, and their exceedingly great prosperity.

Prosperity is a blessing and a curse at the same time. God tests us as much with prosperity as he does with afflictions. In fact, of the two, prosperity is the bigger test. Afflictions tend to humble us and drive us to feel after God. Prosperity, on the other hand, feeds our pride and gives us the confidence that we do not need God. To turn to God in afflictions is a natural, predictable response. To stay with God in times of prosperity is a rare feat that requires great dedication and faithfulness.

Helaman 11:17

And it came to pass that in the seventy and sixth year the Lord did turn away his anger from the people, and caused that rain should fall upon the earth, insomuch that it did bring forth her fruit in the season of her fruit. And it came to pass that it did bring forth her grain in the season of her grain.

Note that the relief of the drought was not instantaneous. The rain returned in the year following the people's repentance, and they still had to wait for the season of grain and harvest. Our sins may leave us with natural consequences that we have to endure even after we have sincerely repented and been forgiven. We still live in a natural world. We cannot expect instant fixes to all our problems. Guilt can be swept away quickly, but consequences may still have to take their natural course. Christ's atonement will eventually right every wrong and heal every wound, but in our natural, fallen world, some consequences are allowed temporarily to persist.

Helaman 11:15

Yea, O Lord, and thou seest that they have repented, because of the famine and the pestilence and destruction which has come unto them.

Repentance is not the same as conversion. Repentance is a prerequisite and a first step toward conversion, but conversion requires more. The people repented because they wanted the famine to end. They had enough faith to believe that God would stop the famine if they would stop their iniquities. They changed their actions, but they did not truly change their hearts. As we read on, we quickly see that it would not be long before they return to their old ways. As soon as the Lord lets up on them, they lose their humility and return to their former sins. When we change just to stop bad things from happening, we leave ourselves in a precarious position. We must go forward from our good start and deepen our conversion. True, lasting change must be more than skin deep. It is a gift, for which we need to work and pray. God will change our hearts if we sincerely desire it.

Helaman 10:4

Blessed art thou, Nephi, for those things which thou hast done; for I have beheld how thou hast with unwearyingness declared the word, which I have given unto thee, unto this people. And thou hast not feared them, and hast not sought thine own life, but hast sought my will, and to keep my commandments.

Nephi's most powerful trait was his "unwearyingness" in carrying out the will of the Lord. We often quote the Savior in Gethsemane, "the spirit is willing but the flesh is weak." Following the Savior, Nephi showed us that a willing spirit can overcome the weak flesh. He was magnificent because he made up his mind to be faithful regardless of the cost, and he persevered. He could trust himself, and God could trust him. We can receive the same blessings that Nephi received if we can develop the same "unwearyingness". It is not grit, however. It is a gift, like faith and charity. If we truly want to be strong, God will make us strong. If we ask with real intent, he will enable us to do whatever is necessary.