Fear or Excitment

I have heard some where fear and excitment feel the same. So what do you do when you are experiencing both at the same time? Logic tells me to go with excitment. Go with the positive emotion. But then there is that nagging feeling that always makes me take a step back. Be careful. Don't set yourself up. So I ask myself what's the difference. Why torture myself with negative thoughts. So what if something doesn't work out. Look at all the time you just wasted on worrying about it. Who knows maybe it will work out. And if it does you really could have just enjoyed your life instead of stressing about it.....sigh Why is this such a hard concept for me........