Tireless
Part of speech: adjective
Definition: Indefatigable, untiring and not yielding to fatigue Without a tire (wheel covering); tyreless.
Example sentence: As a candidate, Obama disdained the game of politics, a self-conscious contrast to all the tireless political athletes named Clinton.
Diligent
Part of speech: adjective
Definition: Performing with intense concentration, focus, responsible regard.
Example sentence: I am very, very diligent and extremely hard-working.