Why am I (33/f) so uncomfortable that my husband (35/m) wants to stop working

Husband of 10 years wants to quit his job and retire early.
We are both fairly high earners. He is making about $150k annual, had previously had investment properties and significant investments. I make about $400k annual, with significant upside over the course of my career, but currently have a little less in investments. We have completely separate finances, no debt, and no children.
He hates working. He has worked very hard to become financially independent, and I love him and I am proud of him for that. Through his investments, he figures he can draw about $50k annually on interest if he retires now, not including his 401k which we won?t touch for many years. He has done all the planning, and budgeting, and I would in no way have to subsidize anything if he chooses to retire. We have already discussed that if we have children, I am more than willing to subsidize that, since he would be primarily caregiver, but we are both ambivalent about children and not actively trying.
I am trying so hard to be supportive, but I am feeling so uncomfortable. I can?t understand why I feel this way, and I don?t want to share these feelings with him. This decision has no meaningful impact on my life, I could easily support us in an emergency, but he has enough that I?m not sure what kind of emergency would even require me to need to dip into my own money.
I guess the question is, how do I even talk to him about this? I don?t really understand why I feel so conflicted about this, and I am proud of him for reaching this milestone he worked so hard for. At the same time, I am really afraid of what will happen if he stops working (but what could possibly happen?? This must just be anxiety??)
In before anyone asks, both of our finances are completely protected if we were to separate.
Edit to add - We rent in a HCOL city, but our split rent is well within his budget. We aren?t looking to buy a home anytime soon.
He is on my health insurance already, and that?s not a significant expense for me.
We both own our vehicles (we are frugal) so no car payment. Our expenses are fairly low, considering.
We did a post nup a few years ago when he started talking about this, alimony is no issue. His whole philosophy is he made enough money that he doesn?t have to rely on me, and the only condition under which I would subsidize is if we decided to have children, in which case my income can comfortably support us.
We have a very even split of labor in the household. I don?t have any expectation that or any desire that he would take on more just because he?s not working, especially since our finances are separate. I really don?t feel remotely overwhelmed by our household labor at all. He would not be retiring to take care of our household
Tl;dr: extremely worried about husband retiring early, want to figure out how to talk to him about it without being unsupportive, but I don?t really even understand why I feel so uncomfortable with it


Source.