Feeling not good enough.
It's funny how, no matter how much you can rationalize that your manipulative advisor is trying to make you feel inconsequential and replaceable,
and the "colleagues" in your field are all socially awkward, self-centered and weird,
and the grad students in your department are all saying they'd work with you if you had your own lab
you can still feel like a complete and total failure when your western blots stop working and you still don't have those papers published in time to apply for jobs.