Sitting on the floor.

I have decided to sit on the floor when I'm at home watching TV. I tried it last night, sitting on my folded-up yoga mat. It was OK at first, but got a bit tiring. I want be able to increase my sitting-fitness enough to be able to sit through an hour episode of something without having to lean on anything. It's supposed to be better for you for flexibility and stuff, and it's active sitting which is better than just blobbing.