I completed my PhD in neuroscience at a mid-tier university.

One piece of advice I can give you is to stay focused, but keep sight of the freedom and flexibility your time as a grad student will offer you.

I was lucky to have an advisor that granted me flexibility to learn topics outside of his expertise through self-study and collaborations. That flexibility ended up shaping my early career.

The last quip I’ll give you is to prioritize your physical and mental health. Go to the gym/run/exercise, meditate, and eat enough. Grad school is difficult, and peripheral health issues make it worse.

Your work is nothing if you don't become part of the community. As much as the lone genius meme can be appealing when you're a PhD student, academia is the realm of anonymous reviews, grant-based survival and kafkaesque bureaucracy. If you don't fit into a research community which will give you support, that's all you'll be left with. That and a stack of worthless papers.