Depersonalization/feelings of emptiness -- I do experience those occasionally because those are part of BPD, but they've gone down significantly over the years and I have a pretty stable life right now.
The bad thing for me is if I'm well rested/not anxious I'm usually not interested in doing anything at all; it's just my hypothesis that anxiety is my high-functioning mechanism for my ADD.
While on certain stimulants (they're not all the same) things just click and I am very calm, zero chatter in my head, I feel a bit dumber than usual, but I also can just focus and do meaningful things. Other stimulants make me euphoric and while I can focus I can easily end up focusing on the wrong things; on other stimulants I'm more anxious than usual, more driven and still better able to focus; unfortunately I live in a country where adults cannot receive stimulants period, let alone find a psychiatrist who's willing to play with stimulants/non-stimulants, dosages and so on.