"If you don’t like the truth about yourself..."

From Michael Novak, "On Loving Karen":

St Thomas (Aquinas) wrote, “Of all friendships,
Marriage is by far the greatest.”
I used to tell my classes that,
And say that it is true.
The only thing – I used to warn – is this:
If you don’t like the truth about yourself,
Then don’t get married.
When you live close in,
Illusions are expensive.
So once the honeymoon is over,
Your lover's duty is
To puncture every one of yours —
One by painful one.
My lover pricked an awful lot of mine.
Especially my conceits.

I'm single — never married, so I can't judge with any authority — but that rings true. Is it? The verse is from a poem remembering his wife with love, respect and affection. They were together for almost fifty years.

On Loving Karen | First Things