I was talking to my partner about our respective salaries (I earn at least 30% more than him, and will likely earn more than him for a long time due to our jobs - he's a firefighter with set pay levels while I work in the corporate world in a management role).

I mentioned how weird it was that a guy would get mad if his wife earned more than him - why on earth would you, when you both benefit! His response?

"Probably cos that's the only value they have to offer in the relationship".

That struck me as so spot on. When a guy is mad that you do better than him at X, ask yourself whether that's because he knows it's the only value he can bring.