I will be starting a Mechanical Engineering PhD program at a highly ranked university this upcoming fall. When I first made my decision where to attend, things were fairly turbulent and I was still very unsure what I wanted to accomplish with my research. The entire application and decision process was rough, but that's aside the point. However, as my senior undergraduate year winds down, I've been better able to focus on what I appreciate in life and come to realize I made the wrong decision on where to attend. Rather, I should have attended a school of a similar caliber but with faculty much stronger and more distinguished in the areas I would prefer studying. Neither school is particularly large, so the flexibility to tune research agendas by changing faculty is limited when compared to, say, a large state university. I came to this realization quickly and called the graduate admissions office of the institution I should have attended and was told it was too late to change course. This realization has badly inhibited my ability to focus on anything in front of me at the current moment (finding housing, undergraduate research, finals...) and I'm falling into depression over the possibility I may have just badly stunted my lifetime career potential. This problem has been haunting me for a month now. This length of time tells me it is more than buyer's remorse (I've never had buyer's remorse for more than a week, even for major decisions like my undergraduate institution). I've been ready for change for years so it can't be nervousness over starting something new. I've been confident and become more confident in my decision to attend graduate school, so I don't think that's the problem either. As far as I can tell, I really have mad the wrong choice. How should I proceed? If future goals anything, I don't yet know if I would prefer industry or Academia post-grad and would rather leave my doors open to when I have more perspective.