You drop a pass.

You flunk a test.

You don’t feed the cat.

It might be because you just got your pocket re-strung, or because your brother kept you up all night before the test, or because it’s not usually your responsibility.

Or

It might be because your skills aren’t good enough, you didn’t study hard enough, or because you don’t care enough.

Why did you come up short?

Was it because of something (or someone) else? or Was it because of you?