Thinking positive is essential and something I still struggle with. Figured there was a way around it - guess what, there isn't.
You need it to sustain positive self esteem.
Besides the great stuff mentioned - what helped me at some of my lowest times was my job.
Basically my job started out as volunteer work (and volunteer work is good too) and it revolved around helping someone else.
Anything that takes some focus off yourself sometimes can be a lifesaver. When down ; do you notice how self obsessed we can get?
And that in turn, makes us feel even more miserable, and makes us feel guilty and selfish on top of it sometimes.
Doing something for someone else that truly means something to them, and that gives visible results (a hug of appreciation, a smile, anything that reaches you inside) can save lives.
Seriously, from my lowest points to now and having something to show for it...still the thing that means the most is what I can contribute to others.
It may sound sappy ; but when that happens and you recognize it, it is like seeing your self at the same time. The good part that can give. Cause we can't give what we don't have.