Originally Posted by MicShazam

That probably depends on what we're talking about. Your brain retains it's ability to learn, so you can condition yourself to at least a degree.

That short speech David Foster Wallace gave to some college graduates once (titled "This Is Water") had a huge impact on me. Inside the last two years, I've successfully taught myself to exercise more of an active choice in how I think about the world - getting rid of unconstructive negative, annoyed, angry thoughts. It took months and months of failure, but now I'm serene like a monk except on my very worst days.