Does this make me a bad employee?

I recently told my manager that I was willing to up my hours as summer vacation is coming up and I won’t have school taking up a lot of my time. But something came up, and I may need to put in my 2-weeks. I feel horrible as I just told them that I would be able to work more, but that was also before this situation came to be.
Does this make me a bad employee?
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