I've read on his web site (www.fullcontactpoker.com) that Daniel Negreanu has the same issue. I'd be willing to bet most card players or any type of gambler would feel this way. You get used to a certain level of action and when the stakes are lower you just don't feel the adreneline like you would normally. Myself, I still like to play in a lower buy in game once a week where I live for a couple of reasons, and maybe these reasons will give you something to play for if you ever find yourself at a low buy-in table again. First, I've been playing in this game every week for many months and have become friends after a fasion with many of the regulars, so at the very least we're all having a good time. Second, since the risk to my bankroll isn't great, I can drink, laugh, hang our and really just enjoy playing cards, much more so than if every decision I make is a critical one. Finally, the competition at this game is really quite good so it allows me to work on my game and try a lot of new things, once again without great risk to my bankroll. If I want to try playing a hand a certain way against certain types of opponents I can do it, and if I lose it's not a big deal, I've learned something and havn't lost much.
Just my thoughts,