> It's possible that they'll explain how ... you're letting everybody down
And if somebody says this to you, your inclination is to believe it -- if you're a nice person. But you have to tell yourself: They are letting themselves down. They made their choice; you don't have to make the same choice, just because they do. Their choices don't remove your ability to choose. They are not allowed to choose for you. Ergo you are not letting them down at all. Instead, maybe you'll inspire them to make better choices.
Well said. It's worth keeping this in mind for salary negotiations as well. Sometimes you'll hear an argument that a company can't offer you a certain salary (even though you clearly are worth it) because its far above the average wage for their other employees at your level.
Other people's inability or unwillingness to negotiate what's best for them has no bearing on your right to negotiate what's best for you.
And if somebody says this to you, your inclination is to believe it -- if you're a nice person. But you have to tell yourself: They are letting themselves down. They made their choice; you don't have to make the same choice, just because they do. Their choices don't remove your ability to choose. They are not allowed to choose for you. Ergo you are not letting them down at all. Instead, maybe you'll inspire them to make better choices.