iE1 (body recomp): calorie counting app, tracking everything that goes in, including hydration + sleep, go into an optimized sports programme and give it all I got, keep an eye on optimal macro/micro, applying social pressure on myself... and so on, everything that might have an impact + preplanned schedules and optimized convenience factors to do the right thing, right from the start. After a few weeks, I just stop it. Doing unhealthy stuff again, ignoring all tracking/notes/plans/appointments and even handwaive the social pressure. Also initial investment (sometimes quite significant) = money factor is just something I shrug off in that mood.
iE2 (building software): I have a good enough idea, sometimes even things I really desperately want for myself. I have a vast toolset of mastered tech stacks at my hands I can use right away, can setup good implementation plans, start with shipping "hello world" to production first (me being a devops many years) and iterate quickly. Also include customer journeys and marketing key points right off the gate. Code written to my personal high standards including full testsuites/coverage, clean component libraries, whatever fits, and also keeping an eye on security and performance. I don't even have to worry much about any expensive hosting/operations costs at all at this point. Still after 2 weeks max, I abandon the project... quite often with a working state that actually is good and usable (most MVPs are in a worse state, as they should).
Its like no matter what I do, there are zero issues for me to research a thing and jumpstart doing it the right (as in: best effort research that looks like actually working) way, and then just stopping it after some time for no particular reason. Somehow my brain just can't be forced for an extended amount of time.
Being aware of that, I also tried several things that are recommended to build up discipline, from atomic habits of different flavors to gratefulnes diaries, so far nothing worked. To give you an idea: I am not able to brush my teeth every single morning/evening as a man in my 30s, its more like 5 out of 7 days roughly. Also I have no attention shortages and can comfortably read a full book cover-to-cover nonstop, meditate or keep the focus of a full-day meeting on track with multiple persons in the room trying to derail.
If someone truly had a solution that works in my case, I'd pay a high premium for that with a smiling face. So far, only failures, and a hopeless me.