Made a couple cards for MailMeSomeArt's current theme.
It took me a long time to realize why I like postcards so much, but it's a simple reason: they have a finite amount of writing space.
When I would start a letter on stationary, it seemed like I would never be finished cause there was always another sheet of paper on the box. So I'd run out of things to say or my hand would get tired or I'd have to stop to make dinner, and then the letter never got done.
With a postcard, you have only the space on the back. Period. Then you're done and can resume your life.
Once I switched to postcards, I became a better corespondent. Not good, but better.