>>5 :

>>8 's right.

You either

1. wallow in self-pity and longing for a year before getting better and moving on with life

or
2. Try to get over her now by doing what >>8 said. Picking up a hobby, getting a job, getting a new girl to obsess over, anything to get your mind off her.

Number 2 tends to be a little less harmful and probably a bit more healthy, but people consider number 1 more meaningful (I see it as a waste of time, personally).

And >>1 :
Seriously, you can't draw it out. That'll just make it worst. Just tell him off the bat, "I don't like you. It's not fair to you." He might say "Give me time" and crap. Just keep saying "I'm sorry" and leave him. Him being sad will not be your fault. Him staying sad will be his fault.