I write myself little lists of tasks, even when I'm entirely clear on what needs to be done. It may not feel like a hack, but it sure works like one for me - it's a simple habit that makes a dramatic impact on the flow of my day.

Advantages I notice:

• mental shift in the perceived effort - instead of a full day of indeterminate stuff, instead it feels like a list of small things
• provides clear places for breaks (which also provides an easy way to say "I'd like to do X to relax a bit, but I need to get Y small thing done first")
• helps me avoid getting distracted and working on something low priority
• makes it clear what's getting done (one less cognitive task, also harder to miss items) and kinda fosters a sense of satisfaction as I go

I dunno, really feels silly that it makes such a big difference, but here we are. I don't do it every day by any means (overdoing it "roboticizes" life to an unpleasant degree), but I use it most work days at least, and sometimes to keep up with chores and personal life stuff when I get real busy.