Ugh, this is why talking about poetry is so hard; poems have already condensed, crystallized, cut to the core, so expounding on them always sounds banal. It's finding extra words for something that is currently pithy and effective.
The point is, I like this poem, and the last two lines particularly are what still ring with me, and what make my mind return to it regularly.
Lord, what am I, that with unceasing care
Thou did'st seek after me, that Thou did'st wait
Wet with unhealthy dews before my gate,
And pass the gloomy nights of winter there?
Oh, strange delusion, that I did not greet
Thy blest approach, and oh, to heaven how lost
If my ingratitude's unkindly frost
Has chilled the bleeding wounds upon Thy feet.
How oft my guardian angel gently cried,
“Soul, from thy casement look, and thou shalt see
How He persists to knock and wait for thee!”
And oh, how often to that Voice of sorrow,
“Tomorrow we will open,” I replied,
And when the morrow came I answered still “Tomorrow.”
Lope de Vega; H.W. Longfellow (translator)