You have limited mental resources. If you really want to get stuff done, conserve them, and use them wisely.
One of the toughest things about getting back in shape is not overdoing it to the point that the exercise makes you physically ill. Backing off a little is better than vomiting mid workout, I think.
I’ve spent 2 years getting woefully out of shape. Worse, I’ve spent 2 years losing the habit of regular exercise. So now, I’m not just exercising, I’m relearning the habit of exercise, by practicing the practice.
I finally blew my daily walks streak. Of course, I blew it by substituting a hard bike ride for my walk, so did I really blow my streak?