Mental stressers are first and foremost victims of their own thoughts. If there's a meeting, some people approach it with confidence, while others approach it with anxiety, whatever their ability or the quality of the work they've put in. You risk putting a ridiculous amount of effort into a situation that seems more complicated or more important than it really is.
A brief session of cognitive and behavioural therapy can teach you to clearly identify the reflexes and negative thinking that are causing your stress.
A session with a therapist about stressful situations can completely change your views. What if things weren't really what you make them out to be? How would this realisation change you? You'd soon switch your approach, put situations into perspective and find different solutions other than stressing! Using logical reasoning, you can learn to replace your anxiety with a more positive approach.