Great recommendations, there's also these below which I highly recommend.
Magic of Thinking Big by David J. Shwartz
Psycho-Cybernetics by Maxwell Maltz
I want to make a point clear though...Having and working on your attitude is great but if THAT IS ALL YOU DO IT IS MENTAL MASTURBATION & an escapism. These are supplements you use...you really need to get these attitudes in your body via action.
When I say this, it does not mean "go sarge ___ # of women" it means, immediately start to try to incorporate these good emotions in the body, be it by smiling, watching your mind, breathing control etc. For concrete exercises for these I highly recommend Sean Messenger who has very basic but practical and immediate exercises to run for yourself.
You can't have one without the other, you can try. That ultimately leads to an imbalance though. The two are connected and necessary for each other.
