Thank you all so much for the recommendations!
I already got me The Art Spirit on my e-book-reader and really have to force me to stop reading at all XD
I would like to add another book to this list:
"Psych" by Judd Biasiotto -
I guess it's primarily aimed at athletes, but it provides exercises for mental strenght and more stress resistance to everybody, even to a (now former) couch potato like me. The book let me give my body another try and start to work out again, nice side effect.