You can't teach an old dog new tricks

Meaning

It is difficult to change the habits or mindset of someone who has been doing things the same way for a long time. It is a pessimistic look at personal growth and aging.

Cynical, resigned

Used in a sentence

• I tried to show my grandfather how to use the tablet, but you can't teach an old dog new tricks.
• He refuses to switch to digital banking, well, you can't teach an old dog new tricks.
• The veteran employee won't change the software he uses, I guess you can't teach an old dog new tricks.