I know 'me too' comments are not welcome here, so my justification for this reply is that it highlights an apparent minority of folks here who really struggle with all the standard tools for so-called procrastination and so-called productivity.

I agree about the lizard brain motivation. It seems that checkboxes are a simple shortcut to achieving that motivation for many. They don't work for me, my experience is similar to yours.

I've realised that if I can find something rewarding to enthuse me, then I can tackle a task. And that reward needs to outweigh distractions, it's no good saying I can have two marshmallows later, I'll take one now thanks. So I try to focus on any aspect of a task that I might find rewarding in the present moment, and if I'm lucky it will push competing distractions aside enough that I can get started.

Every. Damn. Course. That I've ever attended has pointed to 'check the boxes' rather than 'find your motivation'. Checking boxes feels like walling myself into a tomb (see other comments in this thread). It's beyond frustrating.

Yeah, doesn't really work for me either - even when I knew that I'd be much happier after completing the task (e.g., cleaning my room), but nope. I'd just sit there, staring at what I had to do, unable to do it. Then I started reading about ADHD and executive dysfunction and it started to explain a lot - at least for me, the task has to be relatively enjoyable in and of itself for me to do it. The prospect of a reward afterwards doesn't change that and doesn't motivate me to do it. Now I take medication and it's made a noticeable difference to how difficult it is to do unenjoyable tasks.

I have the same difficulty: I can't bargain with myself that way and, ultimately, I feel like I'm acting as both a parent and a child at the same time.

I basically won't get something done unless I actually want to, or if there is an element of external accountability, but sometimes I can encourage myself into it if it feels like unburdening myself.