The reason behind this is another concept that is generally known as resistance of self-sabotage.
Out of fear or doubt, we tend to do things that deliberately sabotage our personality and our future.

Once you get over the fear which is illusionary the actual event is never as bad as we think it will be.

We are programmed to resist the unknown and it's that that keeps us from reaching our full potential.

Amazing choice of pictures by the way!