The misery from the work expressed makes me think this will not be a very long-lived habit. I think in order to get the endorphin rush (or, more accurately, a

The misery from the work expressed makes me think this will not be a very long-lived habit. I think in order to get the endorphin rush (or, more accurately, a general increase in a well-being feeling over time), you need to have a level of intensity higher than just walking. So if you run instead of walk your calorie burn is 4-5x more so you can play this calorie game with even less time investment and you'll get the endorphins that will help reinforce the behavior better.