It's not a discipline thing, IMO. Sounds to me like you need stimulant medication (layperson here, so feel free to grain-of-salt these experienced opinions). Sounds like your brain is seeking out stimulation/dopamine and is attempting to get it through the "unhealthy" (i.e. exciting/fun/feelgood/dopamine-releasing) things you mentioned, especially when you say you always want to keep doing it (ADHD brains require constant stimulation, that's why adhd people need to take meds all day, every day, to function as normal).

I know what you are saying about the smoking and wanting to smoke more. When meds are working as intended, the desire to smoke is sooo diminished. Like, meh, that's okay let's smoke later, I am going to keep working on this I don't need to burn right now... instead of aaaah I just need to smoke where's the bowl, let's smoke another and another, I can't think of anything but smoking right now, ah! (complete with that chest-stomach longing-to-do-______ feeling) It just doesn't even come up as a thought/desire because the brain is already stimulated by adhd meds. Had the same experience with eating tons of sweets and also with not wanting to do ANYTHING boring/effortful/not fun/lame/time-consuming.

It's kind of magical. Also infuriating due to all the years of wasted time and thinking I was just a piece of shit person that couldn't do anything right or function like a normal person, like I so totally wanted and tried so hard to do but just could not do it. The failure and sadness led me to the doctor's office, and that's when life changed and started to get better. Good luck I hope you find your solution.