I have a theory about how to be a good Christian. As with all my ideas, I worry that I've missed something, so please think critically about what I'm writing. But so far I've had success and haven't found this theory to be contradictory to my other knowledge of God and the Bible.
A long time ago, Moses et al summarized right living by publishing the Ten Commandments. Then Israel went on and built a lot more law, most of which is also attributed to Moses - hence the "Law of Moses".
Then a long time later, Jesus came and summarized the law in two commandments:
You must love [God] with all your heart, soul, mind, and strength.
...
Love others as much as you love yourself.
Mark 12:30-31
This was great and I and others find these commandments a useful guide to how to live as a Christian. But there's a problem: Paul came along after and introduced a lot more commandments! Jesus also dropped a few tidbits that don't fit nicely in here (e.g. "Give the Emperor what belongs to him and give God what belongs to God.")
I've been Christian for a while, and I continue to evaluate my actions through prayer and Bible study. Often, someone will share an idea about how to live as a Christian I haven't heard before. Sometimes those ideas don't match with my existing knowledge of God, and upon further reflection I discard them as incorrect. Other times, these ideas do cohere with my experience of God and with what I'm reading in the Bible, and I adopt these principles as my own.
I'd like to enumerate and analyze all things I've learned about being Christian, both from the Bible and from wise people in my life. But it would take a long, long time. So instead I'll jump to my theory that unifies how I live as a Christian.
The unifying commandment that I've been finding useful in gauging the morality of an action is this: how does it affect my heart?
For example, if I toss money to a homeless guy and keep moving, sometimes I feel cynical about it. This isn't good for my heart.
If I use giving money to a homeless guy as a catalyst to getting to know him better, sometimes I end up giving him no more money, and other times I end up buying him razors so he can shave. The act of building a relationship with the guy, regardless of the exchange of money, is good for my heart.
If I become the executive director of a charity and maximize number of children saved while keeping administrative costs low, but never interact with actual kids, this probably isn't good for my heart. I imagine I would feel insulated from reality on the ground, and regardless of the good I"m doing the world, it wouldn't be good for my heart.
If I work or volunteer as a front line worker at a charity, give too much, and spectacularly burn out, that's also not good for my heart (although the first few weeks/months/years probably are good for my heart).
If I give 7% of my income to my church and charities (and diligently track this in a spreadsheet), and feel blessed to be part of God's provision, this is good for my heart. This one is especially interesting because tithing also makes me more conscious of God's provision for me, which again, is good for my heart.
This is all not to mention more obvious examples of good and bad behaviour - these are typically good and bad for my heart respectively. What I find this rule useful for is discerning what to do when it's not clear what's right and wrong, and also discerning why I don't feel good about certain "good" things.
Another bonus of taking the "is this good for my heart" approach is that I end up focussing more on what I"m doing, rather than what others are doing. I can't tell what's good/bad for someone else's heart unless I know them really well. Is alcohol sinful? Not for me, but it is for others. I get to focus on myself.
I'd love to hear thoughts about this, especially about whether it's a Christian idea or not. I have a suspicion this concept comes up in other religions too.