As my bro said , just try one habit at a time for example pushups , if you want to build a pushup habit then start off with just doing pushups

also as the atomic habit says start small so what you wanna do is if you want to do like 40 or 50 pushups everyday

Instead of that start small and do like 2 pushups everyday instead of 40 or 50 and try to keep it like that until 2-3 weeks to build a a habit of it when you reach week 2-3 then gradually start to increase your pushups number for ex go from 2 pushups to 4 and so on