i just want to ask that while in practice matches i play so very well n i just don't know what happens to me in the match im not able to play the way i used to .... please suggest me some useful tips please!!
I can only guess why you can't play at your usual level at the competitions - maybe too few competitions? You are just not used to such pressure, not yet.
The best way to overcome this is to compete more and give yourself some time.
Maybe thinking that competition is just another form of practice might also help.
But, if you are already an experienced player I'd suggest you visit a sports psychologist - they might have some good ideas to help you.