Deadlines.

Self-imposed deadlines can be useful, when the work is something you actually really want to do. Last month when I set myself the challenge of writing every day, having that daily deadline meant I prioritised the thing I wanted to do (writing) above almost everything else. This is especially useful for giving yourself licence to push the mundane but time-insensitive tasks (such as vacuuming the house) to the bottom of the to-do list, although, of course, those tasks all have to get done eventually. And setting writing as a high priority meant I was more likely to do it earlier, when my brain was at its freshest and the ideas could flow freely.
On the other hand, deadlines are far less fun when you don’t have any say in them. Right now, my course (the Computer Science MSc I’m currently studying) feels like one deadline after another. For me, deadlines are a great way to make sure the work gets done, but at a cost of enjoying the work far less (and stressing about it a lot more). I get why assessment is a necessary part of education, but I would appreciate the time to just enjoy learning. It makes me think about my son’s education too. Next year (the last year of primary school) he’ll be doing his SATs, with all the stress of revision and exams that involves. It feels like too young an age to get bogged down in all that, to worry about being judged when learning should still be fun.
As a web developer, all my best learning happened (and still happens) without deadlines. Later on, once I started giving talks and writing articles, I still learned a lot. The process of doing those things certainly helps consolidate learning, exposing gaps in my knowledge and sending me down new rabbit holes. But the stress of having an externally-imposed deadline prevents that part from being fully enjoyable. The fun part (and where I feel I learned the most) was being able to tinker, try things out, and play. I’m looking forward to having some time without deadlines soon.