Giant!

Can't get him/her out of your head? Well, this is what a speaker, in one of the talks or seminars I have attended, said.

Just as the line "you can't do two things at one time" or "you can't serve two masters at one time", your brain can't think of two things at one time. So, if you're thinking about someone(A), in that instant, nothing else is in your mind but him/her. Moreover, if you're thinking of something/someone else(B), the former someone(A) is vanished in your mind. But if you keep thinking about A all the time, your mind will never think of anything else but A and he/she will be a giant in your mind. You will be afraid to fight against that thought and probably think, you can't live without him/her.

Thus, the only solution to your problem is...think of something or someone else. Keep yourself busy. And most importantly, do it now or else, that someone will become a giant in your tiny head. (That's the speakers idea, I don't know what's right and this remedy is not only for those who have hard time forgetting about someone.)