OP here, that's where I started 3 months ago. What I recommend is starting with the most foundational habits - the ones that are preventing you from doing the most things - and moving up from there. This might feel like a waste of time if you have much bigger problems in your life, but the way I see it, if you're already at rock bottom, unless you turn around those little things preventing you from progressing, you'll just sit around for another 3 months not working on your bigger problems anyway. You can't run a marathon in a day, or something like that.
My theory with these cards, and so far it's paying off for me, is that if you establish a solid habit, then you never have to think about it again, and you can do it without spending energy on it. No matter how small your goal is, no matter how many days you miss, chances are you're still doing at least a little bit better than you were yesterday, and as long as you can focus on the tiny day to day progress, you'll get really far before you even realize it. My therapist described it as, when you walk over a patch of grass enough times, eventually it creates a path. It's the same with your brain. Do something enough times and your brain creates neural pathways for it. You got this.
Feel free to post your cards in here for accountability. Thursday is actually the official "share your cards" day on the subreddit, so it's a wonderful day to start!
Pic related is my card as of today. A solid week of flossing and brushing! This week, I experienced something interesting. In the past, I wouldn't even brush my teeth before bed or anything because I'd feel so sick. This week, even if I was sick, I had the willpower to force myself to the sink to brush and floss anyway. Oddly enough, after brushing and flossing most of the time I've actually felt much better. Small steps!
Any other gems out there starting any cards? How's your progress going? Pics are always encouraged.