Brain fitness... I need some help.?

I believe myself to be a pretty intellectual guy, I read about parasites in my spare time, I'm learning French, and Physics; for fun. Recently I picked up a book on brain teasers - to increase IQ, and I'm having a really hard time with it. I'm curious if there are any mental exersizes to reduce the anxiety and stress that I feel from these little buggers; an influence that is damn impossible to focus on these crazy shapes, and ridiculous designs. It clouds my mind, and it's unable to do anything, when my goal was not to regress mental health, but to improve it. So... What can I do beforehand or during that will make this easier to handle...? I really don't understand why these would make me feel this way, but not anything else that my brain is doing. I can't for the life of me figure out why these problems are creating such a difficulty to think clearly while focusing on the shapes at hand.