Why do we fill our life with doubt and uncertainty?

Doubt and uncertainty why?
This is my opinion In our conscious mind we are battling the uncertainty with in our lives , relationships and career. That creates doubt in our conscious mind therefore creates unhappiness that’s so we believe even though we think we are happy. Truthfully if we have no doubt or uncertainty in our lives we have no fear we have just joy and happiness. Doesn’t matter what’s going on around us screaming children so many noises but we do not hear them is in our mind we are balanced clear and happy with all our surroundings. So many times I hear clear mind is a happy mind, it is the truth.
There’s an exercise that I have you all, get a chalkboard and do the chalkboard test that screeching chalkboard noise that everybody cringes when they hear it. Most people cover there ears because the noise is so painful within there conscious and subconscious mind. Trying this exercise and ask your self how you feel. Wright your feelings down on a piece paper then ask yourself why or why not this is so painful to hear.