Oh, I totally hear you on the 12 hours not feeling like enough. Since my tegretol has been increased I am SO BAGGED, that there are morbid moments when I feel you may as well toe-tag me, lol! Sometimes it's hard enough to get up enough energy to eat or take a shower. BUT I DO IT. I agree on the "go out for a stroll" solution or yoga/stretching--nothing major. Mostly I just pick up the mail just to get some fresh air. If I feel up to driving I'll grab a java, etc. I make lots of "dates" with friends to just "hang."
If fruits/veggies agree with you, eat lots of them because you will feel energized. I've started herb gardening again just for the high that watching things grow and smelling them pro-offers.
Stockpile books, magazines...put on the tunes...this will alter your energy field enormously. I suspect that you are surrounded by too much silence and the silence will put you straight to sleep.