(Although this going to start out like one of the woe is me posts I've made a habit of lately, keep reading, it's not)
Don't fall in love with your best friend. Don't. I don't care what rationale or thought you have, it won't work. So seriously, just don't.
"But shouldn't the person you're in love with be your best friend?" you might ask. Yes, but they should become your best friend as you're falling in love with them. Not ahead of time.
It will make the pain of seeing them with someone else even worse. You want them to be happy as their friend, but the jealousy and insecurity will drive you insane. People will want to protect you from someone who already has your back more than they do. People will say things about them meant out of love and defense for you, but you'll hate that they're talking about your best friend like that. People will pick sides in a battle that doesn't really exist.
It'll turn into a giant emotional mess basically.
I'm done. I've tortured myself for a year and a half over someone I was convinced I should be with (and part of me still is). Instead of crying over what I don't have, I'm concentrating on the fact I've got a fucking incredible best friend. A best friend who's always on my side. A best friend who is an amazing mother. A best friend who curses like a sailor. A best friend who can drink dudes under the table. A best friend I can talk to about anything, even how upset she's made me. And really, how awesome is that?
I'll just overlook that whole not knowing a Beatles song thing.