Depends.
As a sufferer from depression, low moods have a whole new frightening level of possibilities which don;t exist for non-sufferers.
I have to accept that i will get 'down' days because that is part of the human condition, but for people like me, there is always the fear that it is the start of something fdar more serious.
I work on the assumption that all will be OK, and I spend some time alone if I can - I usually retreat to the bath where i can get some peace without worrying my familiy.
If not, I will skirt around my music collection, avoiding anying with 'memories' and finding nice easy material that will relax me. A good sign is if i can read - that means things are not getting serious.