I take Seriphos "as needed". When I can feel my thought racing and my blood pressure raising (signs of high cortisol) - I pop a capsule of Seriphos. It usually works in 30 minutes or less. If I am still anxious, I take another. And another if necessary. It usually works but sometimes I can get VERY anxious and need a few pills.
I also strongly recommend trying this Theanine Serene with Relora (by Source Naturals)
It has a strong blend of magnesium, GABA, holy basil, theanine, and Relora... all help relax the body and lower cortisol. You can take it alone or with Seriphos just fine. 1 Seriphos + 2 Theanine Serenes should noticeably calm and relieve alll but the most intense high cortisol state, in my experience.