One peril of living alone is that it becomes very easy to indulge in self-destructive behaviors with no one to check on you.
Eating poorly; sleeping poorly; having too much dust, filth, or random junk around the house; not going outside; not exercising enough; not getting social interacting in the minimal needed amount, obsessing over the wrong aspects of your work.... This sort of things.
Although perhaps less likely, these problems can also easily happen, if you are hanging around the wrong influences.