Idiom: You can’t teach an old dog new tricks - You cannot make people change their habits or character; it is very difficult to change the way a person does something when they have been doing it the same way for many years
Students are in English class
Terry: Hi, Sal. What’s wrong?
Sal: Oh, hi Terry. I’m just really tired. I’ve been trying to show my grandpa how to use his new smartphone, but he is really being stubborn.
Terry: What do you mean? Smartphones are great!
Sal: Well, he wants to return his smartphone for an old-fashioned flip phone. He says that he cannot even use the smartphone. It’s too hard!
Terry: Well, he is not used to that new technology, so it’s all probably confusing for him. You should probably just let him get an older phone he knows how to use.
Sal: I guess you’re right. You can’t teach an old dog new tricks!
Terry: Yes. He will be much happier with a phone he actually knows how to use.
Two friends talking about fitness
Sara: I’m so tired!!
Pat: Why? You aren’t working full-time right now.
Sara: Well, my fitness coach told me that I should start getting up really early around 6 AM. He told me I would feel much better and get more things done.
Pat: What time do you usually get up?
Sara: 10 AM or so. I’m a night person. I love staying up late!
Pat: Well, if you are used to getting up at 10 AM, I don’t think you are going to be able to get up at 6 AM every day, especially right away.
Sara: I guess you are right. You can’t teach an old dog new tricks. Perhaps I’ll compromise and get up at 9:30 AM instead!
Meaning: “You can’t teach an old dog new tricks” means that you cannot make people change established habits of behavior or character. In Context 1, Sal’s grandpa cannot use a smartphone, no matter how much Sal tries to teach him. In Context 2, Sara thinks she can start getting up much earlier than she is used to getting up. In both contexts, it is too difficult to change their habits.