Go slay some giants.
Write a novel? Sing an opera? Discover a new country?
Just do it.
People will laugh at you. They want to minimize anyone that might make them feel silly. They don’t want to face their own forgotten dreams. It’s easier to do that if everyone else does the same. It’s easier to mock those people that still have their dreams. It’s easier to mock the giants and think they’re not worth slaying.
Your dream is worth the laughter.
Your dream is dangerous. It’s dangerous to them; it makes them realize how small they are for rejecting their own dreams. Your dream is dangerous to you; it will lead you to enemies who want to see you fail. And your dream is dangerous in and of itself; any dream worth pursuing will lead you into danger.
Your dream is worth the danger.
You may fail. You might find your dream is impossible after all. You may discover a new dream along the way. You could find something better in the journey. That’s ok.
Go tilt at some windmills.