Reflect upon your blessings, of which every man has plenty, not on your past misfortunes, of which all men have some
Charles Dickens
Life goes not backward nor tarries with yesterday.
Kahlil Gibran
Waste no tears over the grieves of yesterday.
Euripides
All the best things that I did at Apple came from (a) not having money and (b) not having done it before, ever.
Steve Wozniak, Apple