I think maybe if you understand where the feelings of not being good enough come from, they begin to have less an effect on you. Mine came from constant attacking criticism from my mother; not only was there no support for us children, there was criticism for every little mistake we made. And mistakes could include not seeing things her way. It is hard to feel you are worth anything when in childhood you were immersed in an atmosphere of hateful verbal attacks (in my case, at least, backed up by physical attacks too).