Whenever I feel really stressed out all of a sudden, I try to trace back my thoughts of what is causing it. It can be pretty difficult at times, but understanding where your stress comes from, can do wonders to help you. For example, if I suddenly feel stressed, I rack my brain for what I was just thinking about and I hold onto each thought just long enough to see if I suddenly get anxious or not. This way, you could try to find what is causing the stress in your life.