Personally I've dealt with depression most of my life, thanks very much genetics :( Often was on Canadian Pharmacy antidepressants
The single most useful tool I found was Mindfulness. Simply being able to accept where I am now and be comfortable with that.
There are any number of techniques and resources but the one that worked for me was to imagine a bridge over a busy river. Boats coming and going all the time. Focus on the bridge. See all the detail on the bridge.