If you don’t intend to cheat anyone, the party you’re interacting with gains in a similar “amount” as you
If you achieve personal gain at the cost of someone else, their net gain will be even greater than yours
In case there’s no direct party you’re interacting with while gaining (such as you running a red light when no one’s around to be inconvenienced), society as a whole gains
Any and all personal gain becomes mutual gain.