I believe if we really want something we'll find a way to make it happen. It has happened in my life many times. Even if in the beginning you don't see how it can become possible, but you keep the idea in your head and more important - in your heart, there will be a way to make it possible. I have seen so many amazing stories proving that.
But what I have just thought - what if you really want something and you actually do something to make it happen and you even see different ways to make it happen, but you fail again and again. Some would say it's a sign that this is not going to happen, so give up on trying and switch to something else. Ok, I'd have thought so too. But I have seen examples when a person would try and fail, try again and fail again, but didn't give up and this person is actually very happy now because finally all the attempts were paid off. :) And it's not just one example.
I personally think we should never give up, but what if you just spend your whole life on trying to get something you are not supposed to get..? And you end up wasting time... And when is this point that you should realize it's time to stop trying?..