Negative thoughts and waves of despair are the sort of friends you find at the bottom of a bottle of wine or beer or spirits. I remember sitting night after night as I got steadily more drunk and wishing I had done more with my life, and then never doing anything with the life that I had sitting there with me and desperately waiting to be enjoyed. What a loser I was.
But now when I look back I celebrate all the positive things that have happened to me, and that I have achieved; and despite the fact I am now too old to do many of those things I wanted to do when I was young (such as fly in the Navy or go to space), I plan with a sense of excitement all the things I can still do. I never had time for any of these wonderfully positive thoughts when I was still drinking, the alcohol was always in the way and holding me back.
Now I have such clear and lucid thoughts and such a tremendous sense of freedom - if I close my eyes I can fly wherever I want. It's not quite the same as a genuine trip to the ISS, but you know, the feeling is just the same!