No, You dont have to quit your present job for bitcoin. You can do it both, your present job at day time and bitcoin after your work. Because you will never know if until when the bitcoin is but your present job and if you are regular then you can be sure to have it until your retirement. So i suggest to choose both.
It can really be done simultaneously, why quit your job if you can do both. The value of bitcoin seems to be decreasing more. It may not also be permanent, we never know what will happen next.