I found that using a calendar or some kind of tool where I can add a mark every time I do something I want to form an habit of, it helped. Especially with the fact that I also add my mark even if it's only 5 minutes. So it reduces the pressure tremendously if I fail, or change my mind.

I moved from being mostly sedentary to being able to run 10km, swimming regularly, joining a field hockey team, doing archery. I also do hiit 3 times a week. Still my schedule is fucking chaotic, so beside the field hockey training which is on a fixed date, the other activities are done at, let's say, interesting and random time.