What most wives fail to realize is that their husbands' philandering has nothing whatever to do with them.

7 seconds sound clip from the The Philadelphia Story movie soundboard.

You can hear this line at 00:53:53 in the Blu-ray version of the movie.

Quote context

[...]

- Stop it instantly!

- I can't help it. It's sickening.

- As if he'd done nothing at all.

- Which happens to be the truth.

- Anyway, it's not your affair, Tracy. If it concerns anyone...

- Well, actually, I don't know whom it concerns except your father.

- That's very wise of you, Margaret.

- What most wives fail to realize is that their husbands' philandering has nothing whatever to do with them.

- Oh? Then what has it to do with?

- A reluctance to grow old, I think.

- I suppose the best mainstay a man can have as he gets along in years is a daughter. The right kind of daughter.

- How sweet. (2)

- Oh, no, no. I'm talking seriously about something I've thought over thoroughly. I've had to.

[...]