It has been my experience when the thought of failure has not entered my mind, I have experienced the most success. I guess this could mean that thinking of possible failure results in thoughts that subconsciously place barriers to our success. This is another reason to focus on the steps you are taking toward a specific goal and not about the ultimate outcome. In other words, it is good to have goals but best not to focus on the goal.
You are capable of far more than you can imagine.