Oh I see. Interesting article. You may be right - you may be living a high stress life. Of course normal stress in unavoidable. Certain things that come with civilization, like rushing around in traffic, trying to make a buck, keeping up with responsibilities, etc., can add up. Add to that sedentary stress like video games or maybe even stressful movies, and then staying up late partying - I can see what you mean. Especially if there's academics or work piling up too.
One thing you might want to do is to track your blood pressure to see what kind of activities may be causing it to rise. You can get one for around $30 at a discount store I think, maybe even less.
Other than that, don't hesitate to get a check up.
But yes, if you really wanted to lower stress, you could try yoga/meditation, long walks in scenic places, take up painting or music or attend theatre and symphony performances, plus a regular program of vigorous exercise with sunshine and fresh air to keep your spirits up.
As for the effects of cortisol on the brain: people in very stressful occupations (police, emergency room personnel, soldiers, etc.) would then exhibit mental effects. We see this in PTSD among soldiers. It would be really amazing if it turned out to have a preventable chemical cause (supposing there were a pill to limit cortisol production). But I also wonder what other problems are this group inheriting: early onset of dimentia? Attention or learning deficits? Depression? A lot of that could go unnoticed.