Have you encountered any new changes in your life recently? Or
has there been any loss? You could be feeling mildy depressed, if
that's the case.
Or, have you been stressed and overworked over a long period of
time? That would cause you to burn out.
Perhaps, you just need to get a new hobby or develop some new
interests. It might also help if you go out more with your
different groups of friends or even, make new friends.
And hey, if it's new friends you need, might I suggest you include
our outings in your agenda? 
