This may sound a little harsh, but the only thing that gets you playing is a love for the instrument. I'm not saying that you don't love it, but if you don't love it enough to play six hours a day then nothing is going to help that. Personally i don't feel you should have to force yourself to practice. However, I'll also add that six hours a day is a ton of guitar, and many great players never played that much a day. I can admit that I don't play that much, nor would I want to. I have other interests in my life besides guitar, although guitar is definatly the biggest. One needs inspiration as well as just practice. If you are practicing the right way for an hour a day, you will improve, simple as that. Depending on the person, that level of improvement will vary.

And while I'm sure that there are some people who play six hours a day straight.... well... I find it hard to believe that a lot of people do. Maybe they factor in the time they spend on breaks and having a snack and reading guitar magazines and stuff like that...

Bottom line: have fun with the instrument.