What was the biggest pill you've had to swallow about your own self or habits?
I'll go first...after 10 years of speculating in the market (read: gambling in high risk assets) I realized I shouldn't ever touch a brokerage account in my lifetime. A monkey would have made better choices than I did. Greed has altered the course of life many times over. I am at an age where I may recover from my actions over the decades, but it has taken its toll. I am frugal and have a good head on me, but having such impulsivity in financial instruments was not how I envisioned my adulthood. Its a bitter pill to swallow, since money is livelihood of my family, but I need to "invest" all I have into relationships, meaningful moments, and fulfilling hobbies.
That not only am I not a good person, it's mostly impossible for a person to be truly good. Even knowing what good is, in its entirety, is nigh impossible. The best that can be done isn't necessarily within my energy and/or skill.
There are wrongs that cannot meaningfully be righted.
Doing a little good some of the time is the most I can ever aspire to.
So what happens when two people in the same or similar situation define the same action, one defines it as good, the other as evil? It's pretty easy to construct a situation where each person feels morally justified in killing the other.
I didn't say it was a moral system, I never even used the word, it is human psychology and philosophy. Even in your example I could say "This was was to liberate X" then someone else says "That war killed so many civilians!". Someone fires a bunch of people to save the rest from losing their jobs, the fired people say it was bad, the others it was good. Same event, two views. You can have "Hot summers are perfect", the next person hates them.
That's Jesus' "why do you call me good? Only the Father is good". You can never be perfect nor infallible, of course, but maybe you'll be good enough and God will approve of you and that's all we can work towards. No need to use this understanding to give yourself moral allowances though: let your mistakes be mistakes and not plans for immorality.
While it may sound similar it's meaningfully different. Jesus' statement asserts that good is an attritibute that can be had by some being, just not you or me. I am asserting that good is not something anyone can be. There's no deity involved here.