This life is temporary. It is not the end all be all of existence. As the spirit children of God, we chose to come to this earth and experience good and evil in order to become more like God. When Satan tempted Eve in the Garden of Eden, he tempted her with a truth and with a lie.
Genesis 3:1-6
1 Now the serpent was more subtil than any beast of the field which the Lord God had made. And he said unto the woman, Yea, hath God said, Ye shall not eat of every tree of the garden?
2 And the woman said unto the serpent, We may eat of the fruit of the trees of the garden:
3 But of the fruit of the tree which is in the midst of the garden, God hath said, Ye shall not eat of it, neither shall ye touch it, lest ye die.
4 And the serpent said unto the woman, Ye shall not surely die:
5 For God doth know that in the day ye eat thereof, then your eyes shall be opened, and ye shall be as gods, knowing good and evil.
6 And when the woman saw that the tree was good for food, and that it was pleasant to the eyes, and a tree to be desired to make one wise, she took of the fruit thereof, and did eat, and gave also unto her husband with her; and he did eat.
Here Satan told Eve that she would surely not die. That was a lie. Eve had never experienced or even knew that liars existed. She believed the words of Satan. Eve didn't even know what death was. But Satan lied and told her that she would not die. But Satan mixed this lie with an eternal truth. He told Eve that her eyes would be opened and she would be like the Gods, knowing good and evil. We know that this was true because later in Genesis 3 God tells us:
Genesis 3:22
22 And the Lord God said, Behold, the man is become as one of us, to know good and evil: and now, lest he put forth his hand, and take also of the tree of life, and eat, and live for ever:
Here we learn that by partaking of the forbidden fruit, man was able to progress and become more like God. They came to know good and evil. This temporal life became an opportunity for mankind to learn to become more like God by experiencing good and evil and learn to choose good over evil of their own free will and choice. God is a being who has free will and has learn to choose good over evil continually. When we are given free will and placed into a situation where we can choose between good and evil we can learn to become more like our Father in Heaven and our Savior Jesus Christ. This experience is temporary and eventually we all will resurrect and never die again. We will also not be subject to hunger and thirst and fatigue. Only in this life do we learn these things to give us knowledge and understanding and the chance to resist evil and choose goodness. The knowledge and experience we obtain in this life will carry on in the next life and we will be all the much wiser because of it. We will look back upon our experience on this earth and see it as an opportunity we had to gain knowledge and understanding and a chance to become more like God.