From my experience, the most rewarding pursuits in life have been practices. And I don't mean scheduled sessions leading up to games, meets or other sporting events. I mean the regular endeavors that define a person.
I have several that I maintain, two of which I'll write about here. One is journaling, which I do not so much to document my day, but as a meditative practice on what I did and how I can do it better. Filling those notebooks and seeing them neatly lined on a shelf gives me a gratifying feeling. Though the accounts contained in the pages are often unvarnished criticisms, the sheer volume is a testament to progress.
My newest practice is Jiu Jitsu, which I've been steadily doing for eleven months now. For me, Jiu Jitsu, especially as a white belt, is a practice in humility and failure. Modern life and society insulate us from both. But it's impossible to stay in your comfort zone when someone twice your size is trying to dislocate your shoulder. Yes, you fail. Yes, you get humbled. You tap out more than you get submissions. But more important, yes, you get better.
But inherently -- though progress, humility and comfort with failure are all enriching -- the best part of any practice is that it is infinite. The journaling doesn't stop at the last page of the notebook. There's another waiting to be filled. The jiu jitsu player doesn't stop training when he or she reaches black belt. There is always more to learn, more variation to explore.
Practices are infinite. They take us as close as we will ever get to immortality. A practice is an art that imitates life, for the sake of art and life.