How can you stop the “I’m too old for this” mindset and encourage individuals to pursue what they like, challenge themselves and try new things?

We only live once; ask yourself, if not now, when? You surely could not do it last year! It may sound cliché, but there are thousands of excuses not to do what we love. Sadly, one of them is age, and we have all managed to make a big deal out of it. So was gender not too many years ago.
We have to fight against these beliefs. Like Kathrine Switzer, the first woman to run a marathon, people physically attacked her. She didn’t stop. She ran on. If there’s something that you think you could have done ten years ago, there’s nothing to stop you now.
Take the first steps, and face the challenges, but don’t feel like they only exist because of your age. If they do, figure out how to overcome them. I don’t know about the numbers, but many senior athletes became athletes after 50 or even 60. Every year people attend universities in their 50s.
Many people start their successful businesses after they retire. And do not see age as a disadvantage. After all, you are full of experiences.