Be grateful a lot

Because you have a lot to be grateful for. And because being grateful makes you feel happier.

Remembering to be grateful for what you have serves two very good purposes:
1) it makes you appreciate all that you have, and NOT take it for granted. When you appreciate something you value it more, and you take better care of it (this goes for animate and inanimate objects)
2) reminding yourself of all that you are grateful for helps you put things in perspective when you hit those grey days and are feeling blue.

Having gratitude as a habit means that that feeling of gratefulness for what you DO have will be closer at hand when you need it.

Expressing gratitude is easy: start an email thread with your own self with the subject line THINGS I AM GRATEFUL FOR. Then you just reply to yourself each day or week, and when you need a bright thread to grab hold of on a gray day - there it is, labeled in your inbox, a list of reasons to feel grateful.