We all endure a certain amount of stress. Depending on what's going on in your work and in your life, you may be going thru more stress than you want. Not all stress is bad (setting an ambitious goal, for example, adds a kind of good stress) but too much stress can slow you down.
How much of your stress are you choosing? Certainly, not all of your stress, but could you admit that some of it is the result of you doing too much worrying, or waiting too long to work on that big goal, or taking what the boss said too personally, or procrastinating when you knew the deadline was going to be tough?
You know as well as anyone else the answer to what to do about the stress you cause yourself: let it go. Stop it. Relax, breathe, focus, and then get to work.
When we do that, when we control the stress that we can control, when we choose "no" to a piece of self-selected stress, it makes handling the tough unchosen stress much, much easier.