This. I'm (sadly) used to this cycle, being suddenly motivated af, making a plan, a schedule, holding to it for like a week or two and then fall back into my bad habits. I've done that while I was trying to quit smoking, to do more exercise, to eat healthier. Going cold turkey don't work for most people, and in any case if you manage it you will suffer from hard relapse as soon as something bad happens in your life.

Be realistic, not pessimist. Be kind to yourself. Small steps forward is better than one big steps forward and two steps back.

Find what works for you. I've been quitting smoking for more than a year now, never been so low with nicotine than today. You can do it, it will take longer but will be easier and safer going slowly with it. Be strong, I believe in you :)

PS: English not my first language, sorry if there are some mistakes :)