"Never give up" is a phrase I hear a lot. It's intended to be encouraging, and spurring you on to your goal.
"You can achieve whatever you can dream" is another phrase, which though well-meant, is in my view potentially even more damaging. For example, I dream of scoring the winning goal for Fulham in the FA Cup Final against Man Utd. It's never going to happen. I dream of walking on Mars. That's not going to happen either. OK, maybe these are ridiculous examples, but I receive a stream of messages from people who have a dream that involves TV or radio, and want me to help them achieve it. The most popular one is "I want to be a Blue Peter presenter". I say that's fine, and ask which elements of the dream most appeal. We then look at a way that those can be achieved, without reaching an unattainable (for all but one or two) objective. My first bit of advice is usually "Find a local hospital radio station and offer to make the tea". In other words, learn the trade, work hard and look for opportunities.
In my role travelling the world as a professional speaker, I have become friends with some remarkable people, who have achieved amazing things, and now earn a good living as speakers. I count W Mitchell (who suffered 65% burns and paralysis ), Alvin Law (who was born without arms) and Nigel Vardy (who climbs volcanoes after losing most of his fingers) as friends who I admire enormously. They all agree on one thing: there are some things they now can't do, but thousands that they can.
My point is that encouraging people to pursue a dream that they can't possibly achieve is unfair. We can all achieve astonishing things, but we can't do the impossible. Sometimes the best approach is to shrug, give up, and find another dream.