Maybe you have a case of “the grass is always greener.” 1 million dollars a year is a lot. Couldn’t you pretty easily save up and take 5 straight years off if you wanted? What’s to stop that from happening?
Fear. Specifically, fear that I would walk away from that kind of income forever and that I could become destitute in the future (I have a weird relationship with money, having grown up rather poor).
You've played the money game smartly and won. You just don't seem to realise that yet. You've described fear of poverty instead.
Can I respectfully suggest you to consider seeing a good psychotherapist if that's not yet the case? A therapist can help you conquer your fear. Please do read my suggestion in the friendly way I wrote it!