Damn, $400K is a lot of income. I'd have trouble walking away from that as well! One of the reasons for me would be the issue of sunk cost. In order to make that much, you and your wife must have had to invest a lot of time and energy in your education. Maybe work a couple more years and see if having a higher stash makes you feel better/more secure or about the same as now.
Hopefully you realize it's a good problem to have!
Yes well of course lots of people invest a lot in their education, end up with PhD's and don't make anything close to that much.. But the point is well made, walking away from that kind of firehose of cash is hard to do.
Part of the problem though is "high income" is a law of dimishing returns as the taxes are probably eating you alive at that level.
The OP does not say what the value of the house is (is that net equity included in NW, or do you have to take out some for mortgage payments?) and how much is spent on maintenance, HOA fees (I just gouged my eyeball out saying "HOA" out loud), RE taxes etc etc.
It was mentioned above that you really need to figure out what your real cost of living is. As an example, when my Wife and I actually measured what we spent for a year it was less than $30k.
So as our NW (including house) is close to about $2.4M then what the heck are we working for?.. we still do some work BTW, but not because we need the money.
Secondly, the cost of healthcare, when you quit if you have after tax savings your income can be $zero if you want it to be... But actually you need about $24k of income to get enough to be covered by the affordable care act and get maximum subsidies.
The cost of HC is very reasonable with max subsidies.. at least until Trump gets into the Whitehouse!
Look at taxes.. a married couple with no kids can make $20,600 and pay zero Zero Fed taxes... The State taxes (at least here in Oregon will still nail you for about 9% on everything, minus about $700.. But still a very small number.
To answer the OP's question.. its hard to do.. I wasn't making $400k but I still earned pretty well. In fact as I was brought up by Parents that did just about everything wrong you could do with money I have a deep seated fear of not having enough.
I have discussed it at length in my blog if you are interested in my journey.