I do believe that the vast majority of the stress that we experience is self-inflicted. In my particular case, once I realized that the stress was self-inflicted, and I could choose to have this stress or choose not to have this stress, it because a lot easier to deal with.
Now, there certainly are cases where the stress is not self-inflicted (job loss, death of a loved one, etc.) and these have to be dealt on a case-by-case basis. But I recommend looking inward for solutions.