How about the idea of going out for a walk and greeting some of the first people you meet with "good morning" (and a smile). I find that I feel alive after getting a reaction from someone else - especially if they smile back and look like they mean it. So many people around here walk around at speed with their head down, looking like the world is against them. By you noticing them, and smiling, you often get a nice, positive reaction.

So, that's two good things at once - exercise and a nice feeling of being alive. If it's a sunny day, that's all the better.