I think it might be just you. But then, I'm a student, so I have little experience with typical workplaces at all, never mind the ‘old workplace’, whatever that was like. But I do know something about this, as I take drugs for clinical depression every day (and several times a week, drugs for ADHD). Antidepressants don't really cause persistent euphoria once you've been on them for a couple of days or more. I take an atypical antidepressant called Bupropion, which is a pseudostimulant (it also helps with my ADHD, and that means I get to take less methylphenidate, which I like to avoid taking), so my experience is probably different from those experiences of people who take SSRIs. Nonetheless, I feel very much ‘like myself’ on my anti-depressant medication. I don't think most people would describe me as ‘cheerful’, and certainly none would say I'm a ‘positive’ person, although I like to joke and play. I have several friends who are also prescribed pharmaceutical treatment for depression, and you probably wouldn't be able to pick them out from a crowd because of some strange, numbed, or overly happy-seeming behavior. Anti-depressants aren't really happy-pills.
That's why I instead call mine ‘my don't-kill-yourself’ pills.
Again, just my 2. A lot of people are on different drugs, and even among people I know personally I've seen very different responses to the drugs I take.