It is true that if you do not graduate from high school, or you don't go to college, or you don't earn an undergraduate degree, or you don't get a master's degree or (whatever) you will have doors closed on you. You can limit your opportunities by living in one city or another. You can be turned down from a job for having less experience than the employer would prefer...
Still, having only a GED as your educational certification does not disqualify you from being successful. You may find that you have to work harder and apply more of yourself to gain success, but you most certainly can achieve success.
Even if you earn a degree or (whatever) you are not entitled to a certain salary or guaranteed to make even a living wage.