why?

why does it feel like that when one opens one's heart, it feels like one is standing on the edge of a precipice of unknown depths ..... you feel afraid of what is to come or what one finds at the bottom ..... yet the excitement of the feeling of flying into space --- of being so free --- is so,so, soooo very tempting ...... just as the feeling of the unknown, the element of surprise makes you take the leap anyways .....