Dropping caffeine has made me healthier, full stop. I sleep much better now, and I'm no less alert for it now that I've adapted to not constantly having this stimulant in my bloodstream. My physical activity levels have been constantly ramping up; now that Rakeela and I both have bikes, we're going places more, and that's good for us both. The addition of a Dance Dance Revolution set should help me get some extra cardiovascular work in as well; it's a game, but it's also exercise equipment, and I intend to treat it as such.
So the habit I'm dropping now: soda. I'd mostly shaken it two years ago, but slowly ramped up my intake of such in the interim, back to Microsoft's abundant availability of such- a "perk" with distinctly negative health effects. That and a tendency to snack throughout the second half of the day; I'm reminding myself again to eat only when hungry, not habitually- the thing that got me 40 lbs. overweight two years ago in the first place. (I'm stil lighter than that now.)
So the best way around that? Almost-water, and lots of it. Crap with artificial sweetener doesn't count. (I agree with Bill Nye's take on it: it's stupid to go out of your way to drink something carefully tuned to have no nutritional value whatsoever.) Carbonated water with fruit oil (and no sweetening)? Bring it on. Herbal tea that isn't "decaffeinated" so much as "never was caffeinated in the first place"? It works too.
I think the first sign that I'm really on the right track again was my briefly considering whether or not I wanted a root beer today since I had a relatively small lunch, and then deciding that the effects of that much sugar at once weren't worth it.