Success is not the key to happiness. Happiness is the key to success. If you love what you are doing, you will be successful.
Without a good user experience, even the best business model is just talk.
A language that doesn't affect the way you think about programming is not worth knowing.
Always design with the end user in mind; functionality should never be sacrificed for aesthetics.
All things are earth and water that come into being and grow.
I'm mentioning all this -- I'm mentioning all this because I think this is not merely a personal problem; you may think I'm wrong in this, but I think we live in an age when our lives are regularly punctuated by career crises, by moments when what we thought we knew -- about our lives, about our careers -- comes into contact with a threatening sort of reality.
The best way to find yourself is to lose yourself in the service of others.