Woody Allen wrote a very moving tribute to Diane Keaton, you can access (free subscription required) at this link. The whole piece is worth reading, but this part in particular really blew me away:

As time went on I made movies for an audience of one, Diane Keaton. I never read a single review of my work and cared only what Keaton had to say about it. If she liked it, I counted the film as an artistic success. If she was less than enthusiastic, I tried to use her criticism to reedit and come away with something she felt better about.