A good friend was a swimmer on his high school team. Every time someone on the team seemed out of sorts in practice, the coach used to tell them a story about a jar of marbles.
Every competitive swimmer has a jar of marbles, he said. Every time you came into practice and didn’t give it your best, you take out one marble out of the jar.
If this happens a few times, you won’t notice it when you compete. Losing a marble or two doesn’t make you much worse – not immediately at least.
However, if that becomes a habit, you will lose half the marbles in your jar over time. And your competition will destroy you in an actual meet as you’ll be competing against swimmers with full jars, those who’ve given it their all in every practice.
The marble jar story had a simple moral – “Don’t half-ass things. Whole-ass things.”
A good lesson for life.