The Four Weddings & a Funeral star admits he's "a nervous wreck" at the beginning of every big film - because the pressure of making the project a big hit is almost too much for him - and that often makes him ill.
Grant reveals he's tried everything but still struggles in the days leading up to the first scenes of a new film.
He tells the Globe magazine, "The bigger the budget is, the more they're paying you, the more nervous you get as an actor.
"I've tried everything. Yoga, breathing techniques, every pill you can imagine, both chemical and herbal. Nothing has really worked.
"I even had to see a psychiatrist about it. He gave me all kinds of techniques. All of them (were) utterly useless."