People of mature years, who are expected to know better, often do outrageously foolish things, especially regarding romantic liaisons.

The proverbial saying ‘There’s no fool like an old fool’ is first found in a place we might expect to find it, that is, an early and comprehensive collection of English proverbs. There are a few of such but, in this case, it is John Heywood’s 1546 glossary A dialogue conteinyng the nomber in effect of all the prouerbes in the englishe tongue:

But there is no foole to the olde foole, folke saie.