Biblical Purpose
On the highest authority in heaven and on earth, Jesus told us to go to every ethnic group to preach, baptize, and teach people to obey all that He commanded us. What could be more fulfilling than doing that?
Furthermore, Jesus told us to seek first the kingdom of God and His righteousness. What could be more important than doing that? He told us to lay up treasure in heaven rather than on earth. What could be a greater treasure in heaven than the people who believed God because we took the time to tell them about Him?
Loving God
The greatest commandment is to love God with all of our heart, soul, mind, and strength. If love is not maximum feeling but maximum commitment, then knowing God, obeying Him, and telling other people of His magnificent glory is a natural outcome of our relationship with Him. He is glorious and His glory must be made known to the ends of the earth.
Loving People
The greatest expression of love is laying down our lives for the sake of other people. I'm not talking about being a doormat for people to trod on but about intentionally dying to self so that other people may live eternally. The greatest gift one person can give to another is the light of the knowledge of the glory of God in the face of Jesus Christ.
Making Disciples
Teaching people to obey all that Christ commanded us is the second greatest gift we can give to another person. As obedient ambassadors of Christ they will spend the rest of their lives bearing much fruit to the glory of the Father and laying up treasure in heaven.