The dividing line between a dream and a goal is something that takes time and experience. And that realization will shape the way a person's perspective will change as they advance through life. It's wholly personal and no matter how much us older folk try, there really isn't a way to convey it.
You can get multiple chances to reach a goal.
You're lucky if you get one chance at a dream. Most won't ever get more than a fleeting glimpse, let alone a chance at it.
All we can do is cheer people on that have a chance at their dreams. Because giving up on ours destroys our souls.