How can one combat ageism mentally?

I have suffered from ageism so many times as far as I can remember. I was so depressed and isolated. Back then, I preferred not to go out and participate in any social activity, but it was two years ago that I said, “That’s enough! It doesn’t matter if they suppress me or make me feel useless; the only thing that matters is me and how I believe myself.”
Instead of sitting on the sidelines, I spoke up and attempted to participate in the world. Consequently, I became more positive and surrounded myself with younger people. What I wish to say is that don’t be ashamed of your age; this is only a number in your mind. As soon as you stop thinking like this, everything will change in a way you like.