The first question you should ask is: Why do I have stress?
Sometimes people have unneeded or unbalanced stress, so if that is the case, you should consider doing the following:
1. Cut Caffeine (It'll get worse for like 3 days because of withdrawals, but it'll be better afterwards)
2. Get plenty of fresh air
3. Meditation/Daydreaming/Just not having anything acting upon you (phone/computer/people)
If you have reasons that you're stressed though, the best thing you can do is solve the reasons of your stress. If you're stressed because you have work that needs to be done, then doing the work will alleviate the stress.
Cortisol, the stress hormone, actually causes heightened brain and body functionality at the cost of dampening your immune system. This is meant to be a temporary boost to help solve whatever problem is causing your stress. Long term and repeated exposure can cause the opposite, fatigue and restlessness but with no desire to actually do anything.
So, while I laid out some things that can help solve stress issues if you're needlessly experiencing them simply due to being too "hooked in" to the web or social interactions, if that isn't the problem, you should consider restructuring your life. Changing your schedule and sticking to it can frequently alleviate stress.
If that still doesn't work, go see a doctor, sometimes heightened cortisol can be a sign of other problems. My doctor had me checked once, and it came back negative, but it was good to know what I was feeling wasn't because of medical problems, it was just because I was double majoring in two stem fields taking 18 stem credits in one semester, leading to me literally just working and sleeping for 5 months straight with only holidays and about 1 free day a month to not work on things.
If you can manage it, stress isn't necessarily a bad thing. It does make you more productive if you can channel it at the appropriate times. It essentially overclocks your brain. I purposefully schedule myself such that I have bouts of high stress times to be highly productive during, but never again back to 5 months of insane stress. That was about my limit.