Most applicants improve the wrong thing.

More volunteering.
Another leadership title.
One more certificate.
Months of work.
And the list of realistic schools does not move an inch.

It is human to improve the part that is easy to improve. It is rarely the part that decides anything. Picture three applicants spending the same month:

One adds fifty volunteer hours to the hundreds they already have. Almost nothing changes.

One turns research they already did into a real result, a poster, a contribution. How the whole file reads changes.

One makes a meaningful gain on the MCAT, the thing that was actually gating them. Which schools are realistic changes.

Same month, three different outcomes, because they improved different things. None of these moves is right for everyone. The whole question is which one matters for your file, and from the inside, effort and progress are almost impossible to tell apart.