Is this something that comes from rumination? If this is the case, remove the trigger of it. ie, stop writing in a journal if you find your are ruminating on how bad things are, etc. Change the routine to your day if you do this at certain times.

Schedule yourself one activity that gets you out each week. It could be a walk to a cafe or even just hang out at the mall and people watch.

Give yourself one task you otherwise wouldn't do each week - and reward yourself for doing it (for me this was a portion of house cleaning)

This is a start.