Rest days are just as important as the other days of training. But why? According to Runner's World Magazine, rest days serve 3 main functions. They prevent overuse injuries, prevent mental burnout, and restores glycogen. The first two are easier to understand than the third. Simply put, your body stores up glycogen and delivers it to your muscles while you run. Once your glycogen is used up, it feels as though your body has "hit a wall" and moving (let alone running) because a burden. Rest days allows your glycogen levels to replenish allowing your body to keep moving.
Even though it is important to take advantage of rest days, it is important to not just sit around and do nothing on these days.
Just like your mind needs to be continuously stimulated, so does your body. Personally, I get bored and antsy when I just sit around and do nothing. It is especially hard once your body is used to constant movement. On my rest days I always go for a walk. Living in a city that is easily walk-able makes this extremely easy! For those who don't, use your rest day as also your errands day. For example walk around the grocery store or park your car a little farther from the entrance. Make sure to stay active. It'll make you and your boy feel better and more ready for the workouts ahead.