Are you going on for the rest of your life, stumbling into respectability and having to be dug out again? Will you never learn you're a barbarian?
Leora says this to Martin in the third section of chapter 20 when Martin is going on about his speech and asking Leora why she had not liked it and why she had told him, on another occasion, that he had spoken to much. This is important because attempting to fit in is Martin's grandest fault. Martin is an "outsider" from the beginning, as many laboratory scientists are—he is an outsider at social gatherings and he is even an outsider in medical school and in the medical world at large. Nevertheless, Martin tries to fit in and is constantly tempted by success, power, and the praise of those that surround him. It is not until he is able to give this temptation up, not until he is able to give up his urge to fit in, can he truly concentrate on his real work.
Also important to this quote is that Leora knows this and, aside from all of the above, this quote points to Leora's understanding of Martin and her ability to bring him to where he is meant to be. Although, at the beginning, she is why he has to give up the lab in order to become a doctor in Wheatsylvania, in the end, she understands him and his need to research and is ever supportive of these needs.