Perhaps the one who most needs and deserves your friendship right now is yourself. The only rational/healthy basis for any kind of relationship between two or more individuals is for mutual benefit.
Humans possess needs and desires that demand fulfillment and these can create problems for us when we allow them take over and control us. Acknowledging this is the first step in taking control of them and directing them toward goals that are in our own best interest and will provide us with some personal satisfaction and respect for our need to make our life a worthwhile experience.
Sometimes the best we can do for those we care about is to leave them alone and let them live their lives. A relationship that leaves both parties unhappy with each other is an indication that this is the case.
Perhaps once you have regrouped with yourself, you will find there is a basis for continuing some kind of a relationship with your "best friend", but don't neglect the needs of your most important best friend, yourself. Take a break, get some rest and let yourself catch up with the you that has something of value to offer to someone else.
Just a little friendly advice I hope will help. Anyway, thanks for asking.