Who said that? It wasn't Yeats anyway

This 'quote' sits on a wall in Sligo beside a primary and a secondary school. I hope the teachers tell their pupils that it is very unlikely that W.B. Yeats wrote or said these words. The quote has also been attributed to the Greek writer Plutarch but nobody knows for sure.
If the pupils learn anything from this it should be, don't believe everything you read or hear.

Just getting back to the photo - why did they put a waste bin beside the quote!