Well for starters, losing the mentalities "well if I got paid x when I was a junior, then this junior should also be paid x" and "if I'm a senior earning a, this junior should not be earning more than b" when you reach leadership positions will help.
Having profit-sharing schemes when you run your own business are also helpful. Another alternative would be reserving a sizeable proportion (like 20%) of your company's shares strictly for employee ownership.
Absolutely this. Income is not zero sum. Someone else fighting to earn more should be incentive for you to do the same, not villainize them as "greedy".
You cannot be greedy in salary negotiations. A company will not keep you on staff if you demand to be paid more than you are worth. If someone can get paid more by fighting for that raise you should be there supporting them 110% and fighting your own battles to be paid justly for your productiveness.
And you cannot feel guilty about the millions who struggle on substantially lower incomes. It is a problem way larger than an individual that only a small fraction of the working class produces trillions in revenue while the rest make close to parity with their productive yields at fractions of what the top end make. That being said, its not something to ignore, but at that scale its social and political. You have to fight the fights in the arenas they are suited for. Avoiding your own right to the fruit of your labor because your labor produces substantially more revenue than someone elses contributes to holding everyone back when competing for just wages.
Having profit-sharing schemes when you run your own business are also helpful. Another alternative would be reserving a sizeable proportion (like 20%) of your company's shares strictly for employee ownership.