A profession's enemy

Every profession has its own enemy.
To a researcher, it is always time. Time is never enough.
To an engineer, it is always strength. Everything designed must be stronger.
To a doctor, it is always death. A death count ruins reputation.
To a teacher, it is always patience. Patience is a virtue.
To a construction worker, it is always health. The working environment is never ideal.
To an assassin, it is always ego. Ego exposes everything.
To a champion, it is always 2nd place. 2nd place is never good enough.
To a slacker, it is time. There is just too much time to waste.