On, Do You Presently Trust Christ for Your Salvation?

In a particularly ominous statement on eternal security, Wayne Grudem asks what your response should be when God asks you why you should be let into heaven (in Systematic Theology, p. 803):

If I were to die tonight and stand before God's judgement seat, and if he were to ask me why he should let me into heaven, would I begin to think of my good deeds and depend on them, or would I without hesitation say that I am depending on the merits of Christ and am confident that he is a sufficient savior?

The difference between those two answer is razor thin and, at the same time, world's apart.