So how do you respond to a Christian who essentially tells you “I understand the command but I don’t seem to obey it (even when I try)”?
Depending on the person and the situation I could see a couple of different ways to deal with this question. What’s offered here isn’t a verbatim response as much as the reasoning behind the response I landed on:
1) God regularly commands us to do the impossible. Even a casual reading of Scripture makes this apparent. God directs aging Abraham to father a child with a barren wife (Gen 17:15-19). Gideon is told to defeat an army of more than 100,000 with only 300 men (Judges 7-8). Lazarus is told to come out of his tomb (John 11). We are told to be perfect as God the Father is perfect (Mat 5:48). And in our present case, we’re commanded to love our neighbor as yourself (Mat 22:39). To comfort a Christian by asserting that God doesn’t ask us to do the impossible doesn’t hold up under further reflection.
2) Impossible commands can’t be fulfilled by making them more reasonable/attainable. To use just one example from the previous point, Abraham couldn’t assert that God’s word had been fulfilled because he had fathered a child with a younger, fertile woman. Ishmael seemed a logical solution to an impossible scenario but the effort found no favor with God. Redefining the impossible to make it possible may comfort the man but it contorts the message.
3) All things are possible with God. We must remind ourselves that impossible commands are to drive us to the place where we can find the power to do what we can’t do (Luke 18:26-27; Rom 4:19-21; Heb 4:16). His power is at work in us to accomplish all that He requires (Phil 2:12-13).
When our senior adult came with his problem concerning the 2nd greatest commandment, it seemed best to agree with him: he did have a problem with the command and the problem was him. The sooner we see our helplessness the better prepared we are to humble ourselves and seek an enabling power greater than my reason and effort.