Anyone else felt adrift after submitting?

So I submitted my thesis a week ago, and since then I've felt mostly adrift, with nothing to do (I finished the last of my research before submitting) and nothing I want to do into the future. On paper, the PhD went perfectly, finishing in just under four years (normal for an Australian PhD), but in reality I had 14 months sick leave due to mental health issues (MDD, GAD, ED, and some other stuff) that aren't counted, which has left me feeling completely incompetent and inept.

Is this feeling of being adrift normal, or at least common?