Does anyone know the title of the poem by Szymborska which contains a line worded something like “whose life has ever turned out as they thought it would anyway”? I believe that the poem was published in the New York Times Sunday Magazine some years ago.
Although it doesn't specifically contain the line you paraphrased, her poem titled "Life While-You-Wait", from 1976, describes the sentiment expressed in it, i.e. that life isn't scripted and can't be planned, and you have to take it as it comes and improvise. Perhaps this is the poem you're referring to?
Here are a few excerpts, in a translation by Stanisław Barańczak and Clare Cavanagh:
Performance without rehearsal.
Body without alterations.
Head without premeditation.
I know nothing of the role I play.
I only know it’s mine, I can’t exchange it.
I have to guess on the spot
just what this play’s all about.
If I could just rehearse one Wednesday in advance,
or repeat a single Thursday that has passed!
But here comes Friday with a script I haven’t seen.
And whatever I do
will become forever what I’ve done.
From: Wisława Szymborska, "Poems, New and Collected, 1957-1997", translated by Stanisław Barańczak and Clare Cavanagh, Harcourt Brace, 1998. (Google Books link)