I'm in a daze. I'm sincerely worried my acceptance might be a mistake.

I imagine we've all heard the horror stories about mistake acceptances and I'm so scared I'm a victim of it. Of the three programs I've heard back from, I was rejected from one of the "okay" programs regarding prestige level, but today received an email that I was accepted to a program far more prestigious than the program that rejected me. I know that there isn't simply a ranking system at work, but both programs seemed to be an equally good fit for my background and goals, so I can't wrap my head around this being anything other than a mistake, despite the fact that my acceptance wasn't even a form letter, I had to log into my individual portal and there I found a letter with my name in it offering acceptance. It still feels like it must be wrong somehow.

I guess my impostor syndrome will start before I even decide where to go. Anyone else feel this way?