The reason people fail to change their lives, and fail to instill new habits, is because they try to do too much at once. In simplest terms, if your new habit requires more willpower than you can muster, you will fail. If your new habit requires less willpower than you can muster, you will succeed.
You couldn’t do a 30-minute workout because your willpower wasn’t strong enough or was depleted. But you could do one push-up and segue into a 30-minute workout because it only requires a tiny amount of willpower to start, after which your body and mind stopped resisting the idea.
Willpower , it’s a limited resource.