how to prepare and train MENTALLY?

hi there..

long time never post already. everytime when i play some game wether singles or doubles at normal time, i feel quite comfortable and less pressure. i can play all out, play my skills, play my game and always in good form. im sure this is the same thing with everybody.

but the problem is whenever im in tournament or some important matches, most of the time i cant play my usual game. i seldom take part in tournaments. i wanted to but there wont be a lot of tournaments in my area. i will feel pressured and nervous during tournaments. this will cause me to play my game very badly. sometimes, even lower level player can even beat me when it comes to tournaments.

im now currently doing some intensive training because my tournament will be in the end of the year. but all these training mostly include all the phisical trainings like drills, gym etc.. can anyone suggest the way how i want to train mentally? like tell me the ways how to do mental trainings or etc...

thanks answer will be appriciated..