Daily exercise, literally daily with no misses, lowers cortisol if it is moderate as well as consistent. You burn off cortisol using those big muscles as when walking. So a twenty minute daily walk will regulate cortisol to stay low and be burned off easily. The irony is that more strenuous exercise will raise cortisol levels. And days off from exercise will leave those raised levels high as not being burned off. Working horses rested on weekends get horribly stiff from no exercise to burn off high cortisol levels.
The brain must have Choline to feed the Hippocampus sleep center to be able to sleep. Chronic low levels of Choline absent from the diet can actually cause brain damage and insomnia. Choline is found in (gently poached) egg yolks and soy Lecithin. Or take the fraction as a supplement, Phosphatidyl Choline. It is often linked with Phosphatidyl Inositol. Also consider taking the Thyroid Basal Temperature test you can find on the internet. Sleep disorders might indicate low thyroid function best tracked down with this temp test. God bless!