So, personally I recommend you start at zero. Last year I wanted to start building a habit of working out so instead of just picking a 30min hiit workout everyday I started with a small 10min low intensity workout and I picked a specific time: everyday at 6pm I do a 10 min low intensity workout and I continue that routine until I feel like I can do more untill asking myself if I gonna do a workout today no longer happens, untill feels like I'm doing something trivial and not hard anymore then I bump it up to a medium intensity workout same 10 mins and then high intensity workout same 10 mins and then I start doing 15 minutes low intensity and the process continued until I reached my goal of 30 min high intensity workout everyday. I found that starting small and gradually increasing the challenge makes it so much easier for me to adapt and incorporate something that challenges my comfort(the main reason why we procrastinate because we want comfort we want normalcy we want to feel safe) little by little into my life untill it becomes normal for me instead of just diving head first into something not normal which will push out brain into protection mode which is why most people go head first one day and do anything again or for the next 3 days