How to Define a Day Well Spent

I think so often we can reach the end of the day and feel like it's a failure if we didn't get through our to do list or our checklist. So what do we do? I'm imagining I drew this like T-chart of the shoulds on one side, the reality slash what I want and what I'm doing on the other. It might not have been that I checked everything off my to do list, but perhaps you can survey the fact that one particular thing took a lot longer than you expected it to.