The thing about getting older is you don’t have to give up or give in. What you have to do is (quoting Tom Araya), adjust the odds so you win. In the case of training, that means adjusting the variables to account for your age. The biggest problem with older lifters is thinking they are still 18 years old.
Think about what kind of girl you went after at 18; now think about what is important at 59 years of age. Your goal is still “happiness” - but it is defined and gone after in a different way. It’s not a 1:1 metaphor but you can understand where I’m going with it.