Right now your field of empirical experience with the world is very narrow. You're still in plato's cave with regards to all that's out there. You've invested an enormous amount of emotional energy into your PHD thesis program, this creates a strong "initiation effect" on you that might cloud your thinking as to its worth and your actual enjoyment of it as opposed to alternative opportunities, especially if they involve risk of failure.

As for partial knowledge, this has to be taken on a case by case basis. Knowing to wash one's hands to prevent disease is a useful piece of information that I can use even though I'm not a doctor.