What must I do

From Luke's gospel: a lawyer stands us and ask " what must we do to inherit eternal life?" then this man pressed Jesus further on the question because he wanted to "justify himself." I wonder if Jesus and this man had a previous encounter and the man is trying to show Jesus that he was doing what is expected of him by the law! It is difficult not to get in the position of justifying ourself for actions that we believe are right but others perceive as cruel or unjust.we don't want to bethought of as doing wrong when the other person does not know the full story, needs more information or has been misinformed. But the line is thin as what is right, merciful and just and what is merely allowed by law.