I did it folks! Wasn't easy and had a long week of back & forth as they tried to change my mind, but notice is officially in and I'll be out of the job next month. My boss was pretty pissed off and didn't make it easy. The reason I gave was honest, that I'm ready for the next chapter. Maybe that was too vague and hard to process, I don't know. This is only the second job I've quit in my life, so I'm not a pro at this sort of thing and I genuinely like many of the people I work with, so I don't like like seeing them disappointed. But I'm also not an ego maniac and know that they will get on just fine once they accept the change. There's still much to do to sort through making a smooth transition, but the deed is done.
@kook I totally understand your reservations. There have definitely been a couple nights of insomnia as I thought about giving up the golden handcuffs, whether I'm really "ready", whether the math of FIRE is really going to work after this long bull run, etc, etc.
What I kept coming back to is that my heart just isn't in it anymore. My boss offered to increase my salary, negotiate different assignments, and basically whatever would make me happier. But during those sleepless nights as I ran potential scenarios I realized none of it felt inspiring anymore.
I'm not one to sit around and smell the roses (though maybe I'll learn!) and I've been quite driven for the bulk of my life. But what's the point of letting all that energy atrophy? I'm only 54 and have plenty I can achieve/do/enjoy otherwise. And I'm hanging onto a spot that some whipper snapper would probably love and enjoy, which means keeping it is preventing someone else from the opportunity. That just doesn't make sense.
Thanks to everyone here who's contributed to the conversation. I'm excited and a bit scared but I know I made the right decision. Let's see how it goes from here