I suspect.....do unto others as you would have it done unto you
is the key
the material stuff that slips through my fingers is just that
easy come.....easy go
as for treasure in heaven
I might receive as I gave
this way......one gesture to the poor is returned by each participant in heaven
as many participants as there may be
each misdeed is returned.....as many times as there are participants in heaven
So you follow the golden rule not out of regard for others as much as regard for your own self-interest over the long term.
If so, then the thing you're not seeing is
empathy. We give regard to others because we care about them the way we care about ourselves. When I inflict discomfort on someone else, I feel discomfort myself.
I suppose this is also regard for my own self-interest, but it sounds like this is what you're missing here. Inflicting harm on others would cause me pain, so I don't do it. And I don't mean abstract "I ought to recognize the value of this person as a human being and that the world will be worse off if he suffers" ideas - though they're important - causing others to suffer causes literal pain and anguish for me, so I don't do it.
To me, hurting others to get ahead makes as much sense as trying to lose weight by cutting off my arm: yeah, in a narrow perspective it's aligned with the stated goal, but in the broader context it makes no sense and would hurt a lot.
From your questions, I take it you don't feel this sort of empathy. Am I right?