The mathematician does not study pure mathematics because it is useful; he studies it because he delights in it and he delights in it because it is beautiful.
Optimism is a strategy for making a better future. Because unless you believe that the future can be better, you are unlikely to step up and take responsibility for making it so.
I decided, very early on, just to accept life unconditionally; I never expected it to do anything special for me, yet I seemed to accomplish far more than I had ever hoped. Most of the time it just happened to me without my ever seeking it.