I usually feel bad and feel like I don’t accomplish anything if I don’t at least do something productive. Perhaps you should read some books, when you eventually get used to it, reading provides more imaginative stimulus than either TV or other things, and your parents probably won’t complain about you reading. You could also read I am Legend (it’s an actual book). I had fun reading it, I recommend it.
As for being happy, you have to find what makes you happy, everyone has different ranges of what they consider that makes them happy.