My phone has been a lifesaver for remembering things. I grew up in the days of paper planners, so it's a real treat to be able to set up reminders etc. Prior to that I used lists and post-it notes. Post-it notes are tricky because if you use them a lot they become part of the scenery, so getting an assortment and changing to a different color note helped me to notice them.

For developing habits, instead of "do it for 30 days and it'll stick" (lmao) I try to shoot for progressively more consistency over time. So when getting back in the habit of flossing, every day was overwhelming but I could do once per week which was better than nothing. Then every other day. Now I do it daily. Does this work with everything? No but when it works it works. In other words don't let the perfect be the enemy of the good. Some > none.

Mindfulness is not a cure-all but it is a good building block. I practiced just being present and noticing my thoughts. Noticing thoughts allowed me to start observing my train of thought to see where exactly it derails and keeps me from getting things done. If I can figure out where I'm getting distracted I can create workarounds for those. Sometimes I have to literally make a diagram of the thought pattern, like a flowchart, to see what's happening.

I also made a list of my main goals in life including the pedestrian ones like eating healthier and doing creative things, and posted a thing on my fridge to help remember to do something towards those goals every day that I feel up to it. That cuts down on the amount of time I spend in neutral gear wondering what to do with my time. If I don't know wtf else to do then at least I can do something small that will advance a life goal.

The last thing I'll say is give yourself some grace. Nobody has their shit together. Some people just fake it better. Reward yourself whenever you make progress and go out of your way to point out to yourself when you accomplished something or successfully used a cognitive tool. That voice in your head that says you're dumb and can't do anything? It's a jerk, don't listen to it. Go out of your way to rub your successes in its face.

That's all I got, hope it helped.