Friendship is unnecessary, like philosophy, like art... It has no survival value; rather it is one of those things that give value to survival.
Do not waste time bothering whether you "love" your neighbor; act as if you did. As soon as we do this we find one of the great secrets. When you are behaving as if you loved someone, you will presently come to love him. If you injure someone you dislike, you will find yourself disliking him more. If you do him a good turn, you will find yourself disliking him less.