Robust, Palpitate, Mentor

Robust - Someone or something that is robust is very strong or healthy
Palpitate - If someone's heart palpitates, it beats very fast in an irregular way
Mentor - someone who gives them help and advice over a period of time

"You have great potential, but you cannot control your anger well enough, you cannot subjugate it," the mentor's voice was icy calm and almost reluctant. 

"I. Can." said a boy through clenched teeth slowly getting up from the dusty ground; tried to wipe out blood dripping from the corner of his mouth but managed only spreading red across his face; lifted eyes and looked his robust mentor in the eyes and repeated firmly – "I can."

"You can control your actions and won't let your anger take over you, but it is still inside you, burning like hell. I see it through your eyes. Your heart palpitates not because of anxiety of the fight, but because you are angry you aren't as strong and fast as you want to be; your hands are shaking because you want to tear my eyes off, for I'm stronger than you. Today and now you can control it, but it is part of you and someday it will kill you." and with final words the mentor hit the boy sending him yet to the ground again.