Man kann erstaunlicherweise so ca. jedes zweite Zitat im Netz von Bruce Lee hernehmen... er erklärt dir wie das geht mit dem mentalen
und das passt auf alles, wo es MANN GEGEN MANN (oder Mann gegen sich selbst) geht 
Glaubst nicht? Pass auf 
“Don’t fear failure. — Not failure, but low aim, is the crime. In great attempts it is glorious even to fail.” – Bruce Lee
“The great mistake is to anticipate the outcome of the engagement; you ought not to be thinking of whether it ends in victory or defeat. Let nature take its course, and your tools will strike at the right moment.”- Bruce Lee
“Defeat is a state of mind; no one is ever defeated until defeat has been accepted as a reality.” – Bruce Lee
“The successful warrior is the average man, with laser-like focus.” – Bruce Lee
“If you always put limit on everything you do, physical or anything else. It will spread into your work and into your life. There are no limits. There are only plateaus, and you must not stay there, you must go beyond them.” – Bruce Lee
“If you spend too much time thinking about a thing, you’ll never get it done.” – Bruce Lee
“Life’s battles don’t always go to the stronger or faster man. But sooner or later the man who wins, is the man who thinks he can.” – Bruce Lee
Be happy, but never satisfied.” – Bruce Lee
“To hell with circumstances; I create opportunities”. – Bruce Lee
...und noch was weiß ich wieviele mehr... pick dir raus, was dich anmacht!

//EDIT: ach komm, ein paar schieb ich noch nach: 
“For it is easy to criticize and break down the spirit of others, but to know yourself takes a lifetime.” Bruce Lee
“In the middle of chaos lies opportunity” – Bruce Lee
“Mistakes are always forgivable, if one has the courage to admit them.” – Bruce Lee
“Absorb what is useful, discard what is useless and add what is specifically your own” – Bruce Lee
“To know oneself is to study oneself in action with another person”. – Bruce Lee
“It is not a shame to be knocked down by other people. The important
thing is to ask when you’re being knocked down, ‘Why am I being knocked
down?’ If a person can reflect in this way, then there is hope for this
person.” – Bruce Lee