There was a time in my life where I always considered myself to be a piece of shit, and I was always very quick to remind myself what a loser I am. Even after I lost over 100 lbs, I considered myself to be a piece of shit. That's when I realized I needed to make a change from the inside.

I quit belittling myself and my achievements, it took a couple years to break the habit, and start complimenting myself.

I can tell you without a doubt that I'm a much happier person these days.

So, I guess that's my anecdotal evidence in favor of positive thought.