In all of Jesus' teaching, I dare say there is only one moral lesson, and it boils down to this. Amidst all the turmoil and drama of human activity, against all our thoughts and desires, there is very little of value apart from God. Everything Jesus said and did centered on that singular notion. His teaching philosophy was a practical outworking of that living and breathing devotion expressed in the shema. Whatever God happens to be doing or thinking or wanting (or whatever God will be, or might be, or always has been doing or thinking or wanting), according to Jesus, THAT is always the highest principle when considering questions of moral excellence. There was no other lesson.
Jesus did not give out a long list of principles to obey. There was not a rigorously codified ethical system to be put in place. The demoniac was told to go back to his family. The bereaved son was told "let the dead bury the dead." The Nazarenes lost favor with Jesus by rejecting his message of grace to the gentiles. The Syrian woman won favor with Jesus by comparing herself to a dog. The rich young ruler was challenged to embrace poverty. Zaccheus was only asked to host a meal. Joanna followed Jesus around while maintaining significant wealth. Jesus said "yes" should mean "yes" and "no" should mean "no" but he once told his brothers he was staying home and then went to Jerusalem anyway. He rebuked Peter not long after praising Peter. He bought his mother a new home in Capernaum, refused to go see her when the whole family (except Joseph) was gathering, and then made special arrangements for her care after his death. Sometimes Jesus fed people. Sometimes he sent people away hungry.
When people demanded favors, or wisdom, or miracles--aside from whether or not he obliged them or refused--Jesus always raised the conversation to convey a much higher perspective. The man was born blind to show what God could do. The storm kicked up so the boaters could grow in their faith. Jesus beat that trap with the coin by evoking the image of God. He paid the temple tax to avoid giving offense. When Peter rebuked him he didn't say, "How dare you challenge my authority?!" He said, "Your mind is not presently focused on God." Whether by circumstance, segue, or non-sequitur, Jesus was adept at transforming the subject under discussion. The twelve-years-old story reflects someone whose thinking was non-typical. Jesus' own style of non-typical thinking consistently centered around his peculiar obsession with God.
According to Jesus, morality requires one thing: a constant, dynamic, disruptive, transforming, reverent, fearful, worshipful, prioritization of God. There is no rule God respects more than God's own active ruling. That is moral philosophy, according to Jesus, and Jesus did not codify that philosophy, though he frequently illustrated and exemplified it.
According to the Gospels, our best insight into God's morality comes by observing Jesus himself. When the dove landed, God said here's the one guy who's been doing it right! When Jesus finished his "sermon" on the mount, people said they could tell that he spoke from experience. When Jesus prayed, he went away by himself, sometimes by climbing a hill, sometimes by closing a door. Jesus worked with his hands, earned his own bread, gave to those who asked, and didn't worry about his own needs. He was poor in spirit. He sought first the kingdom of heaven. He made peace, loved mercy, and rejoiced in his sufferings. He loved his neighbors, he prayed for his enemies, and he wanted nothing more than for God to rule on Earth, in every human heart. Jesus did all these things because he genuinely loved God with all his heart, mind, soul, and strength.
The rest of us may or may not be capable of living up to the standard of Jesus, but I don't see much point in comparing our relative failures against that ideal score. Instead, I would humbly suggest that we should at least bring proper focus to any discussions about "godly principles" of "christian living" according to Jesus.
You've read the Gospels. Is there anyone in them who condemns you?
There is not. Go, then, and focus on sin no more...