premature celebration 

Throwing a party or celebrating an event before it is appropriate. Most often done in an effort to fit the schedule of someone other than the party honoree.

Kelly: Why are we having cake today? Isn't Cara's birthday next Friday?

Mark: Yeah, but her boss is on vacation next week, so we're having a premature celebration.

premature celebration by Fireball D May 7, 2009

premature celebration 

golf term: The use of any celebratory action (ie. fist pump, raised arm, verbal comment etc.) assuming a putt will go into the hole before the ball actually enters the hole thus causing the ball to miss. Very mysterious phenomenon which plagues golfers.

I had that putt made until Steve went into a premature celebration and caused it to lip out

premature celebration by goodbuddygolfer September 16, 2010