Valerian is a herb that has sedative qualities - it reduces stress and its associated physical effects very good. But don't take too big doses of it, as it can cause some side effects. You can buy valerian in any pharmacy store or order it on Amazon.
Read "A Mindfulness−Based Stress Reduction Workbook"
As you work through "A Mindfulness-Based Stress Reduction Workbook", you'll learn how to replace stress-promoting habits with mindful ones. The skills you adopt will last for a lifetime. The program described in this book will help you relieve the symptoms of stress and identify its causes so that you can start living a healthier, happier life.
Once you feel you are stressed, i.e. you have stress symptoms, go for a walk. It is perfect if it's a long walk, but even a 15-minute one will help you relieve your stress. Better if you go to a less crowded place, e.g. in a park, for example.
What does stress do to your body? Nothing good, that's for sure. This technique will lover your stress level quite quickly and you will be able to act normally again. Whenever you are feeling stressed, try to make your breathing out longer than your breathing in and count while doing them. Make ten breaths like this and you will feel much relieved.
Feeling stressed? Once you feel stressed for some reason, try to think what you would like to do right now, something that is just for you. It can be an ice cream, a hot bath, walking in the park, visiting a museum, etc. Do it right now and you will forget about your stress.
If you are on the relation home-car-office-car-home every day, it is very easy to get chronical brain stress. So make a rule for yourself to find some time for a walk every day. Even if you have little time, you can do it while your break at work, or you can walk after work somewhere in a park near your place. Your brain needs fresh air and relaxation for staying smart and calm, so walking is the best way.