try hard to shift your focus. find something to engross yourself in - a project, a hobby. even focusing on being optimistic in itself will remind you that that is not how you feel and then you'll think of why you don't feel that way. it's not going to help to read about optimism.

yellowted had some good ideas as far as getting into a routine of sorts so you have something to go out and do regularly and may have the opportunity to make friends who have similar interests. perhaps you could volunteer somewhere, or get into a sport you enjoy, or take up a hobby or craft of some sort. doing these things will help shift your focus away from him and onto something more positive in your life.

I had to do this myself a couple years back. I joined a writing group, I have gotten back into swimming, I have started drawing and painting again, I've looked into auditioning with local theaters (but haven't because of transportation problems). doing things you love to do can not only be fun rewarding but can also help you develop relationships with others who have common interests and improve your outlook on life. it won't happen over night, but it can help a lot if you stick with it.

some of my friends from my writing group have become my biggest support people over the past couple years. and my writing has given me another way to process things and express things that I have trouble talking about.

exercise is the most effective anti-depressant there is. it works better than drugs and many people who find drugs ineffective, are recommended to try regular exercise. but it is something that you have to really stick to and do often. I try to get out and swim any time I can (preferably 3x a week) and on days I don't swim, I go for a run in the neighborhood. my husband is a cyclist and rides his bike everywhere whenever he can - he also enjoys playing soccer and tries to do that a couple times a week.