I have noticed this several times that when you do a physical activity, you get a good night sleep. Whenever our body is exposed to too much of work or too much of activity, it always expects good rest. Even when you have a big meal, your body expects rest in order to do digestion. Similarly when you do heavy exercise, your body always expects rest.
I have noticed that whenever I go for a good walk covering some decent steps, I feel like having a good night sleep free from all stress and other issues. When my body gets exhausted or tired after physical activity, all it expects is good rest which it gains from sleeping. I have not had sleeping problems on days when my physical activity is very high. That's one of the greatest things about walking regularly.