Excellent advice for anyone, regardless of physical health or mental stamina. I've found consistent daily habits make a huge difference in my productivity (crucial for a self-employed writer/artist such as myself). It's also so worth it to include exercise or some daily physical activity, as well as meditation, in the goals and not focus entirely on project deadlines and tasks. It's so easy to fall into 'I don't have time to go for a walk' or 'I don't have time to meditate today,' when the truth is that both those activities will help you be more focused and productive and return much higher value than the minutes involved in making time for them during the day.
I can't claim any high degree of excellence sticking to my habits all the time. Like so many others, I tend to do very well for a while and then slip up. Some kind of a checklist or tracking system -- coupled with rewards/penalties can help a lot with staying on track. And simply knowing how effective routine is does help get me back on track when I slip up.
RE: Don't Break the Chain: A Simple Hack for Building Habits and Getting Shit Done