Slept with my best friend....

I've been friends with this guy for 23 years. We have had a lot of trauma together and have been through a lot of trauma together. I got out of a severely toxic abusive relationship. My ex has actually pulled a gun on me and my best friend saved my life. Idk what happened last night. I was celebrating his birthday and some how that led to a make out session and that led to us having sex. I left in the morning and he's been texting me wanting to talk about it, but I can't do it. In all honesty I am in love with my best friend, but that only works out in the movies. It never works out in real life. I can't throw away 23 years for my dumbass feelings. Idk how this whole avoiding him thing is gonna work either....