first to relieve stress and negative thoughts is to stop thinking for a moment, relax, empty your mind and begin to refill with a focus on finding the most sensible way out of the existing state.
Sound advice, most people who are negative are victims from their own mind that creates thoughts that keeps us anxious, worried or even stressed out. Meditation and mindfullness (it rather is mindlessness actually) is a good way to deal with this but hard to do in our hectical and busy society.