Where one wins, another must lose. This often involves scarcity of the "reward". In a school context it could be limited places for universities compared to the gigantic population of people.
At least in terms of time. Where I allocate more time to an activity, I take away from another. The absence of activity, i.e., sleep, also counts as one for the purposes of planning. (But please don't sacrifice it! Please...)
The tragedy that humans compete against each other - it appears on one condition: more people than places (jobs, universities), leading to the need for stupid metrics or subjective judgement of the potential of the human applying for work (and the beginner would be the easiest to fire anyways!)