I agree with Skittles, It has to do with the comparison your brain makes between your manic/psychotic state and your current baseline/depression.
You probably are too socially embarrassed about what happened to you while you were manic/psychotic in a very self-conscious level (i.e. you're too aware of the fact that you were "sure" about your manic/psychotic delusions and they turned out to be false) so now, at least at some basic degree, you can be questioning your own opinions when you try to state them in a social situation.
That's the way I see what happened to me after my second episode (full-blown psychosis). When I had the first one (manic episode) I didn't interact with so many people, so when I came to realize that I was delusional about most of the beliefs that then arisen (that I was, literally, the smartest man on earth), I didn't get very socially withdrawn or felt ashamed as much as after the second break (when I became, literally, God).
My Pdoc once told me that you couldn't have symptoms of ideas that weren't inside you in the first place, so manic/psychotic episodes, the way I see them, are usually the manifestation of exaggerated sprouts that came from little "mental seeds" you already had. So it happens with the aftermath of a break, some seeds you were probably unaware of before (social anxiety, introversion or ambiversion, self-centerednes) sprout.
Some sorrows can't be gotten over, but can be only assimilated.