Cortisol is not a bad thing IMO. Just like estrogen plays a function in the body, so does cortisol.
Look into Addison's disease. It's where the body doesn't produce enough cortisol and the patient has to ingest oral hydrocortisone. Low blood pressure, hypoglycemia.
Our bodies are designed a certain way, and when you mess with these levels, there will be good things that happen, but also bad things. It's just natures way of evening things out.