I can't do everything.
I often start on one project, then quickly get sucked into another project because I've gotten bored of the first or want to learn something new. As a result, I have like 40 unfinished projects lying around in Github repos or folders on my computer.
I should clarify: I haven't learned this lesson yet, but I'm trying to. I'm trying to be a finisher of projects and not just a starter, so I can actually be a productive human being!
Wilferd Peterson calls successful people those with their heads in the clouds and their feet on the ground. I've got my head in the cloud... now I'm trying to reach my feet to the ground.