Well, there is no universal cause of stress meaning that there are lots of them. Besides, it may be a combination of things that causes your stress. Here are the most common sources of stress: being unhappy with some aspects of your life or in general, being unemployed, being sick, having huge workload or working long hours, divorce, losing a job, facing any sort of discrimination once or on a daily basis, moving to a new city or loss of a loved one.
No matter what the cause of stress is, what is important in this respect is to find a way in which the person will be able to tackle that issue. The faster one does that, the less terrible the consequences are going to be. What it all boils down to is that it is of vital significance to accept the fact that you are having a problem and to start doing something immediately. In such a way, you will manage to deal with the cause of stress in your life.