Love is the most important thing! (1Cor.13) That's really the whole purpose for living, to love God and others.--And that means not just to win the lost 'way out there, but to win brothers and sisters right here! The whole purpose for everything is love!
Some of our relationships are directly between us and the Lord, like praise and prayer and obedience, but most of them are relationships on a personal level with each other, and the main lesson we're supposed to learn is to love one another. If we haven't learned to work with others and how to love them and how to treat them, then we're missing the major lesson of why we are here in the first place!
We're not going to grow very much or learn very much unless we learn to have loving interaction with other people, and that's not always easy, it takes patience, love and humility. The Lord gave the simple key when He said, "Do unto others as you would have them do unto you." (Mat.7:12) It takes a lot of learning to learn how to carry that out--and a lot of love! But that's what we're here to learn!
Don't you want to grow?--Then love!