Happiness is a byproduct

The "Quote of the Day" on my Google homepage must repeat every year, because I'm sure I've seen this one before.  Nevertheless, it's so true:
Happiness is always a by-product. It is probably a matter of temperament, and for anything I know it may be glandular. But it is not something that can be demanded from life, and if you are not happy you had better stop worrying about it and see what treasures you can pluck from your own brand of unhappiness.
- Robertson Davies