I always go back to "This is Water" by David Foster Wallace. Not technically a book (It was a commencement speech). I keep the pdf on my phone. Puts things in perspective for me when I'm feeling overwhelmed.
Fantastic recommendation. I got the book version of this for my brother after he graduated high school (or was it college?). DFW really saw through the noise. May he rest in peace.
http://metastatic.org/text/This%20is%20Water.pdf