I know it's hard. Just like others have said, I have found self care activities the best... Cooking, making fresh juice, bought some new pyjamas and skin care stuff. All the things that make me happy and I'm sure you have yours.
The other thing that has helped is amping up the exercise. This morning I was feeling particularly down and preoccupied with negative thoughts so I went for a jog. The endorphins really kicked in and upped my mood. It's taken me years to accept that I have to exercise everyday in order to be happy.