For successful people an important principle adhered to is taking personal responsibility for their decisions and their consequences.
This doesn't mean that we fail to acknowledge actual obstacles that may impede our progression, rather it means acknowledging that sometimes bad things happen -even to good people. The true determinant of success however is appropriately and resolutely responding to life's challenges when they arise.
Though the above description reeks of an overused cliche, this personal approach to life is the antithesis of the default human condition. For this reason many reflexively blame others or "the system" if they find themselves in circumstances that are less than favorable. Why? Its a basic human psychological defense mechanism used to resolve feelings of inadequacy or personal deficiency.
Although challenges do exist that may be substantial e.g socioeconomic circumstance, prejudice, nepotism, discrimination, government malfeasance etc. the accomplished find ways to overcome these obstacles rather than clinging to the alluring yet destructive defeatist / victim mentality.