It is good advice and I didn't intend to belittle it, but it might take a bit more when you find out your wife has leukemia or that your son is autistic or you can't find work in your field or whatever. The strength of a relationship isn't just built on the sense of identity that each partner has.

Take the facial hair case. I know a dude who has a beard and his wife is a little older than he is. He knows she's insecure about this so he keeps the beard because it makes him look older. He's not subverting his identity, he's showing respect and kindness, in a way that she might not even be aware of. His sense of self-identity is enhanced by his recognition that he is in a relationship.

A good relationship won't just let you do you it will let you do you more than you realized you could.