amphet can be useful.
the truth is that most competitors will use some type of stimulant or a concoction as well as other drugs eg roids, gh and epo to get them through fights.
aggression MUST be controlled in an mma fight or you'll tighten up and burn yourself too quick, not to mention you're power, speed, tactics and timing will go to shit.
don't forget stimulants raise the pulse rate too which can be telling when you're doing 3 - 5 5 minute rounds when you must get your pulse rate down between bursts.
the truth is that fighting has alot to do with remaining calm and loose. u should be like a controlled assassin. don't show any feelings, but have deadly intentions. keep your face calm and your eyes alert.
if you get your man hurt or your hooks in, destroy him, but even here you must be calm and methodical.
the referee is there to look after your opponent's health, not you. your job is the opposite.