I feel like an idiot because my fiancee's career and income make me feel like an idiot
What about their income makes you feel so badly?
I'm constantly reminded of how good she is in her work
You should be happy about your partner's success instead of being insecure. Ask her for help on your career instead so you can achieve some too.
You don't know anything. People should not feel bad about who they are or what they have. You are just a piece of shit.
I was just saying that you should be happy that they are doing so well. I think that you should try not to be jealous as their good income and career can be a benefit to the both of you.