It's probably also worth keeping in mind that although those two hours will be in the future, which will (one hopes) be much awesomer than the present, they'll also be when you're old, which will (one frets) be less awesome.
If exercise postpones the breakdown of age, those two hours are right now. It's not like the date of decrepitude is fixed, while the date of death is postponed, like Swift's Struldbrugs.
I see what you're saying, and that could be true. But it might not; an hour of exercise might push death away by two hours, but only delay decrepitude by one (or less).
Or worse, exercise might bring on some early decrepitude, by wearing down joints. (The added life could come from improved cardiovascular health.)
"Cryonics has a 95% chance of failure, by my estimation; it would be downright /embarrassing/ to die on the day before real immortality is discovered. Thus, I want to improve my general health and longevity."
That thought has gotten me through three weeks of gradually increasing exercise and diet improvement (I'm eating an apple right now) - but my enthusiasm is starting to flag. So I'm looking for new thoughts that will help me keep going, and keep improving. A few possibilities that I've thought of:
Pride: "If I'm so smart, then I should be able to do /better/ than those other people who don't even know about Bayesian updates, let alone the existence of akrasia..."
Sloth: "If I stop now, it's going to be /so much/ harder and more painful to start up again, instead of just keeping on keeping on..."
Desire: "I already like hiking and camping - if I keep this up, I'll be able to carry enough weight to finally take that long trip I've occasionally considered..."
Curiosity: "I'm as geeky a nerd as you can find. I wonder how far I can hack my own body?"
Pride again: "I already keep a hiker's first-aid kit in my pocket, and make other preparations for events that happen rarely. How stupid do I have to be not to put at least that much effort into making my everyday life easier?"
Does anyone have any experience in such self-motivation? Does this set of mental tricks seem like a sufficiently viable approach? Are there any other approaches that seem worth a shot?