I recently watched a movie called "Last cab to Darwin" about a man named Rex with a terminal illness. In the movie, they had just made euthanasia legal, except that it was only legal on the other side of the continent (and Rex had never left his small town).
I'll skip to the part about the "big shot"...on his journey across Australia, Rex meets a man named Tilly, who had earned a spot on a major league soccer team, but he entirely blew it off. Didn't go. He had his big break and he didn't take it. Cut to the time of the movie and Tilly, as a result of meeting Rex, ended up getting a second chance for his big break. Again, he didn't take it. He went to practice, did really well, but before his first game, he bailed. I don't want to ruin the movie for you, so I'll just say that having Rex in his corner helped Tilly go for his dreams.
The main thing that struck me about that aspect of the movie was a feeling of sadness and empathy for Tilly...because now I understand why someone would have all of their dreams at their feet and choke. In a word, it is FEAR.
There are many possible reasons for this or aspects around it. It could be a fear of being SEEN. It could be a fear of being "better" than others at something (believe it or not, it's more common than you think). In the end, it comes from our negative subconscious programming that tells us we aren't enough.
And it doesn't have to be a really "big shot" like playing on a major league sports team. It could be that important presentation at work (or even getting up to speak in public at all), or going after your dream job, or stepping out into your own business.
How do you get past this? You have to figure out what is on the tape of your subconscious mind and change it (and EFT is one way you can change it). You can also push past your fear and do it anyway...if you are aware enough to recognize that is what it is...but that is an uphill battle when you are going against your subconscious mind that wants to keep everything THE SAME. It also helps to have someone in your corner.