William Arthur Ward quotes
The pessimist complains about the wind; the optimist expects it to change; the realist adjusts the sails. 
Opportunities are like sunrises. If you wait too long, you miss them. 
The mediocre teacher tells. The good teacher explains. The superior teacher demonstrates. The great teacher inspires. 
It is wise to direct your anger towards problems -- not people; to focus your energies on answers -- not excuses.