Just like a sound barrier we have a barrier that we put on ourselves for how far we think we can go to achieve something.
You don't know exactly what it is but still you stop when trying to break the barrier. It starts to feel uncomfortable and you become possessed on doing something else as long as it stops you from having to break through.
Once you break through you know that feeling of exhilaration the problem is how to get you to break through There have been many saying to get us to do this -
"Feel the Fear and Do it Anyway"
It’s not easy to push and keep pushing when it feels uncomfortable it is suppose to and break through your Mind Barrier!