Many choose certainty over uncertainty, even if the known certainty is a bad situation. Often the certainty of a bad job or relationship, or the certainty of doing things the exact same way again and again is chosen over the uncertainty of changing it and opening the door to something else. There must be something about knowing that adds comfort and prevents us from seeking alternatives, sometimes to our detriment.
This is unfortunate because most great things come from stepping onto the ledge of uncertainty. Pushing yourself beyond where you think you go and risking the uncertainty of failure is the way to experience growth and open yourself to new things. At some point you have to take a leap of faith to give yourself a chance to experience greater things.