i just wanna know! for those people who suffered from this certain thing and eventually recovered from it, please give me some advise.
Tell her/him, if you haven't already. Best way to begin overcoming infatuation is to not let it be your little secret anymore. Infatuation is, generally speaking, a way we indulge ourselves in emotional fantasy.
If it's not a secret anymore, you actually have to deal with it rather than decieving yourself into thinking that you can keep how it makes you feel without the risk of rejection. Bringing it into the light will, if you let it, make you process your own fears and questions of your own significance. It will help you discover where you've put false hope and allow you to ground your hope where you've been designed to ground it - in Christ.
That bit about "tell him/her" may not apply to everyone, but it was always what it came back to when I struggled as a single guy with intense feelings for a girl. It's certainly not a quick fix. But quick fixes are notorious for not really resolving the problem.
Personally in these cases, she (whoever she was at the time) didn't have power over me, and
she wasn't an idol. The idol I was trying to serve was
myself and my own emotional needs. And, like a good idol, it demanded worship. The liturgy or worship I gave to this idol was placing my hope in her to satisfy/mend/complete my emotional needs, something only Christ was meant to do. The result was constantly going back to thoughts about that person, even when on some level I knew it was not good for me. Guess what though - you don't have to keep drawing water from that dry well.
Many, if not most, of the recurring emotional attachments I have experienced myself or helped friends deal with began to be resolved when it wasn't allowed to be a private emotional fantasy. Face your fears of rejection, if you haven't already, and then begin dealing with why you allow those fears to dictate your thoughts, performance, and happiness.
Long process, perhaps. But nothing worth doing happened overnight... the good news is, if you're in Christ, He's not given you anything He's not going to supply the grace to overcome.