This may be a stupid idea, but here's the trick I use to force myself to not sit down for too long:

I drink a ton of water, and I mean a ton. I drink so much that I HAVE to get up every hour (at least) to use the restroom. Usually that's closer to 45 minutes. I know drinking too much water isn't healthy either, but I think I am at a nice balance of hydration.

Does anyone else do this?