There’s no rule book for how to manage this kind of challenge, but in general, you have to try to recognize that when the stakes of a project are very high, there’s not much to be gained from putting additional pressure on the people working on it. Projecting your anxiety onto your team is counterproductive. It’s subtle, but there’s a difference between communicating that you share their stress—that you’re in it with them—and communicating that you need them to deliver in order to alleviate your stress.