“In reply Jesus said”: There were times when Jesus refused to play the game of his interrogators, for example when they asked him by whose name does he cast out demons and when they asked for a sign. But he takes seriously this man’s question even when his intention was to justify himself—clearly Jesus did not want to let the man deceive himself and deprive himself of his own salvation; after all he is so near in his understanding of the Word.
I think the reason why the man stopped after understanding from the Word that life is found in love, is because the scope is so vast and impossible. Jesus supplied the answer: it is to become one who loves—a person who responds with love to the situations they encounter as they live their life—rather than participate in an infinite number of loving actions towards an infinite number of neighbours. The goal is the self.
Of course even that is impossible for man to perfect given his sinful nature but at least it is a goal that he can pursue. The solution that Christ provides in the Gospel is firstly to remove the penalty of failure (though not the consequence in life) and secondly to gift us the Holy Spirit to empower our faith.
For Christians who have the Holy Spirit, the pursuit of love—the faith that makes us determined to obey God despite the obstacles, internal and external—gives birth to the desire to overcome the selfish impulses of sin and do what is right and good and loving, releasing the power of the Holy Spirit so that we succeed in due course. Christ’s sacrifice allows us an infinite number of retries with no penalty in our lifetime.
God indeed is good.