Golden Rule ("Do unto others as you would have them do unto you")
I recently heard a podcast where it was pointed out how self-centric that rule is. Others may not appreciate being treated that way, even if it is how you prefer to be treated.
Better to listen, think of their needs or at least have an attitude of empathy and act in a way that not only does them no harm, but rather lifts them up and encourages them. You'll be surprised that often will feel good to you as well.
Of course it's also important not to disregard your own needs and goals, and if you have a healthy respect for yourself you won't.
At times when your needs and goals seem to be in conflict with those of others, consider it an opportunity to reflect on your needs / goals and see if there's a way to align them not to be in conflict, be it through listening, negotiating or revising your own perspective.
Opportunities for the greatest improvements come more often than not through situations involving some type of struggle. Try to find a way to "not let a good crisis go to waste", not in the Hegelian sense that phrase is typically used, but rather in a positive way that results in a better situation for all involved.
As for Big "T" Truth, I've always held tight to the belief in it, an "absolute" truth separate from anyone's individual perspective, a truly objective Truth worth our efforts to learn as much of it as we can. Mark Passio labels such truth as Natural Law.
But what if this isn't base reality as Elon Musk and others hypothesize? If what we call reality is just a layer of a truth "onion" should it alter how we behave in the layer we reside in? The adage "As above so below" comes to mind, as does the concept of a recursive, fractal universe. If there is an objective, absolute Truth and our layer of it is like others, we may not need to focus on the boundaries or try to understand other layers when the answers we seek are right here in our own layer, and within ourselves.
Many great thoughts here, thank you for your comment.
I've heard similar critiques of the Golden Rule (and the Silver Rule) and I agree with them. Ultimately, we should treat others as they want to be treated in order to increase human wellbeing.
As to not disregarding your own desires, I've really enjoyed learning about objectivism and how, rationally, virtue is a wonderful ideal which maximizes our own wellbeing as we also consider the long-term benefit of others.
As far as I understand of "Natural Law" is that it emerges from what we observe about nature. It's not absolute, but again, a construct which serves us well and fits our observed reality. As you said, we could all be living in a simulation anyway, so any big "T" Truth we might claim could just as easily be an illusion, right?