I was wondering if anyone had any exercises or tips for training or preparing the mind for poker.

Dan Harrington’s book has recently made me far tighter and weaker than I need to be. I’m constantly in fear of my opponents and I can’t help thinking I’m beat. So I’m reading Doyle’s book again in an attempt to revive my mean streak. Dan’s book (Harrington On Hold ‘em) wasn’t a complete waste of time for those interested in getting it and maybe it’ll work better for some people more than others.

So I need to overcome this mental barrier BUT I don’t want to overdo it and become a major donkey. How?

(I've expanded on this below...)