Poker is pacience... and you need pacience to do the job done.
If you don't have pacience you have two choices:
First: Quit poker
Second: Study, Understand that you gonna lose 60-80% of times and just acept that, and keep playing....
You can't be nervous or angry because you made the wrong choice and the man has AK and you AQ and lost. or you had AA and the man pay with 72o and win...
It will happnes, and if you are playing 8-12 tables and lost your mind, you will not just lose one table, you will lose all the tables.
Pacience is everything!