Defining marks of a Christian?

"There are always two things present in the Christian: 1) A sense of personal unworthiness, 2) A sense of the worthiness of Christ. Both are essential. The absence of either means that we are not Christians. But in practice it is the relative position of the two in conscious experience that determines what we do..." - D. Martyn Lloyd-Jones

in David Martyn Lloyd-Jones: The Fight of Faith 1939-1981 by Iain H. Murray