Mormons believe that agency is eternal principle. Agency is the right to choose between good and evil and to act for ourselves. We believe that this was very important even before we were born. In the premortal life we had the ability to choose and we chose that we would follow Christ.
“What is the purpose of life?” Life on earth is a period of testing to see if we will follow Christ and do the things that our Heavenly Father has commanded us. Because we are able to choose, we are responsible for our actions. (see Helaman 14:30-31)
One verse that I really like is 2 Nephi 2:27.
“Wherefore, men are free according to the flesh; and all things are given them which are expedient unto man. And they are free to choose liberty and eternal life, through the great Mediator of all men, or to choose captivity and death, according to the captivity and power of the devil; for he seeketh that all men might be miserable like unto himself.”
The choices that we make here on earth are important. When we choose to follow Christ, it will lead us to happiness and eternal life. When we follow the temptations of the devil, we will find that we become captive in sin and miserable. Though his temptations may seem fun and will make you happy, the consequences will be further separation from God and captivity to the devil.
Heavenly Father has told us in the scriptures how to escape the captivity of Satan. We must watch and pray always, asking God to help us withstand the temptations that we face. (3 Nephi 18:15) We will never be allowed to be tempted beyond our powers to resist, our Heavenly Father won’t allow it. (1 Corinthians 10:13)
As we choose to follow the Savior, Jesus Christ, we will be happy and have eternal life.