I’ve had periods where I’ve really struggled with this too. Before I give my rec, I want to emphasize that I think we all experience cycles in our behavior where we “make progress” (whatever that means for you!) and then we don’t - and that’s really okay. I would start by figuring out if your body is physically okay. Lethargy/fatigue is a biological response to a lot of different things and it may be the result of unexpected health stuff! So don’t discount a doctor’s visit. But mental health/stress really contributes to this for me, and it is often the biggest thing that breaks my healthy routines. This is where the loop comes in: healthy routines combat stress, but stress breaks up healthy routines. So that first day you start the healthy routine cycle is really important! For me healthy routines start with good sleep hygiene. If you’ve been rotting in bed a lot and your sleep cycle is screwed, re-establishing that may be difficult. I would recommend supplementing your body with physical movement - preferably something rigorous (for your level) but also gives you joy!! No boring gym time - do whatever gives you endorphins. Consistent activity is really key for your body to not fall into a doom loop. And lastly, do the things you need to do to combat your stress. Set yourself up so that you feel you are taking meaningful steps towards progress. Start with the small stuff and don’t discount them!!! Often the small tasks are the ones that break us because they seem innumerable (for me it’s always been folding laundry). But just remember, every small thing you do is progress and that will build your momentum.
I believe in ya! You have the power to change this, slowly but surely.