Just like Santiago, many of us fear that our hearts will suffer if we go in search of our dreams. What if I fail? What if I get hurt? But that is your ego/mind talking, not your heart. You must understand where this fear comes from and know that "the fear of suffering is worse than the suffering itself." Fear keeps you from achieving what is meant for you and you will begin to feel the void and the lack in your life if you choose your ego/mind over your heart.
Why listen to your heart? "Because you will never again be able to keep it quiet. Even if you pretend not to have heard what it tells you, it will always be there inside you, repeating to you what you're thinking about life and about the world."
Trusting that you will always be supported is hard to grasp when it seems that life doesn't always go as you planned. But maybe the plan in your head is not the plan in your heart. We experience pain and suffering when we go against our hearts and follow our ego/mind. When we stay in our comfort zone and never push ourselves. This can be applied to any aspect of your life be it work, love, family, etc.
If there is one thing I know and let's be honest, I know a lot ;)...it is that you will always achieve what you are meant to achieve when you follow your heart. Your ego/mind may take you off course a bit, but you always find your way back. Trust in your heart and in your dreams! And if you need a little encouragement, read The Alchemist!