Take on a project ambitious enough that it forces you to work on it to the exclusion of at least something else. The first such project of the smallest such magnitude is probably free since it is probably replacing something you didn't need to be doing anyway.
Some things are best done as one of many simultaneous occupations. Some are best done to the exclusion of almost everything else.
I don't know what I'm saying. You do you. I've got some things coming up I need to be locked in for.