Writing programs that people actually use. I was a hobbyist programmer for a long time. Then my father passed away, and I went through his computer and saw all these projects that would never see the light of day. That gave me the motivation to choose one project and see it through until it was good enough to have actual users. Programming is much more satisfying and meaningful now.
So to me that means that I need to focus and do one thing at a time.
We are a sum of our parts and I probably wouldn't have as great of an appreciation for the time I have left if I hadn't wasted so much time. I still get a lot of time to code, but damn, my single 20s were a whole different world.