It's not necessarily contradictory that someone who spent his life advocating positive thoughts kills herself. In Argentina many cases of priests that are child abusers have just turned up, and I say this to make my point that it's a common human reflex to force yourself to be the opposite of what you desire.
Positive thoughts: I had a friend who was always preaching about the importance of positive thinking, and how through that your life would improve. But in the time I saw him his father had died, his brother was run by a bus, he was shot in a leg, he lost his job, his girlfriend dumped him..But he insisted on this positive thought thing no matter what.
It's a defense mechanism, very poor people lacking resources are sometimes incredibly positive in the way they see things. Some people if they really saw themselves for a second, would have to kill themselves on the spot.
There are lot of geniouses that were very negative, and some commited suicide. I don't see the point of that either.
Rather than forcing yourself to think positive all the time, I would suggest that you DO lovely or interesting things for you and others.