Why time matters more than amount

The uncomfortable arithmetic: somebody who saves a modest amount from twenty-two and stops at thirty-two frequently ends up ahead of somebody who saves the same amount every year from thirty-two to sixty-five. The early years are doing work the later ones cannot catch up on, because they have had longer to double.

The practical conclusion is not "save a lot", which a student cannot do. It is "start small and early rather than waiting to start properly" — because the thing you cannot buy back later is the time, not the money.