Distance urself - listing down pros n cons of turning the friendship into a romantic relationship. Decide whether u want to tell or not - suck it up & move on if the answer is no, tell & be open if the answer is yes - give him space n time to digest ur confession - be prepared to accept rejection, or be happily ever after if he says yes.
SUCK IT UP & MOVE ON IF HE SAYS NO. Cry into a pillow if u need to, but not in front of him - distant urself, take all the time u need to be OK again - be friends again if u can let go of that feeling, stop being friends if u cant.
At the end of the day, if it wasnt meant to be then its not going to be.
Its difficult, but i've survived one. It was messy, but i didnt die!
But the shortcut is even better;
Dont fall for someone first, esp.ur bestfriend.
Just DONT. Full stop!
U know urself, the classic symptoms. So whenever u have that itch of maybe falling for somebody esp.ur bestfriend, simply chant the magic spell " i dont need another downfall".