The fear of "what might happen" is a very strong deterrent for us and has the ability to stop us in our tracks, no matter how much we want something or know that we should move forward. Each of us has heard messages at some point in our childhood that can make us fear what "might happen" and they stay with us and serve as painful reminders of past pain, our shortcomings, our disappointments and our failures. Unless we address and disprove them, these messages stay with us and we unconsciously choose people, situations and even lifestyles that make them true.
(Jennifer Hoffman)
I'll admit that the "what if" mentality plagues me. I often wonder why, but I have few answers.
The main theory I have come up with, as in the quote, is simply relying on past experience.
In my younger adult days, I did not experience failure, therefore, there was no hesitation when it came to the pursuit of dreams.
Failure and disappointments came later in life and it could be that is when the fears were born.
How we think and perceive those thoughts can be very powerful.