Wiktionary
you can't teach an old dog new tricks
prov. It is impossible to change people's habits, traits or mindset.
Wikipedia
You Can't Teach an Old Dog New Tricks
You Can't Teach An Old Dog New Tricks is the fifth studio album by Seasick Steve. The album features former Led Zeppelin bass guitarist John Paul Jones. It peaked at #6 on the UK charts and #18 on the Irish charts.
Usage examples of "you can't teach an old dog new tricks".
They say you can't teach an old dog new tricks, but who would want to?
He goes about the city talking to friends, eating in the central dining-room and mumbling that 'you can't teach an old dog new tricks.