Everyone should know this Shakespeare Sonnet. I used to think Proust was thinking of it when he named his sequence of novels "Remembrance of Things Past." Later I learned that this was the translator's contribution. But, really, that sounds better than "In Search of Lost Time," in English that is.
For the series, I'm trying not to list poems I once knew and have forgotten, but poems that I have permanently memorized, a much smaller subset.