Even if you, due to some event, don't reach your FIRE target or something happens incurring an expense you didn't plan for you are still likely left with a massive financial cushion most folks could barely phantom having available. Even if it derails the plan to such an extent that you have do to something you didn't phantom you are still likely to be massively better of than most of your peers. For high earners it might probably be difficult to return to a similar pay after being out of the game for a long time, but with a big, fat, comfy cushion the need income required should be much lower and flexibility much higher. So even a failure in this particular department still overall means a massive win. Look at it from the bright side if SHTF.
As a side note, when Covid hit and people lost their jobs the newspapers were full of people where the gist of it essentially was that their personal finances were in really dire straits when income suddenly stopped. And this is in socialist Scandinavia with one of the most generous welfare systems around *, but due to the sudden surge in applications they had trouble actually processing the applications and paying people. So the essence of the situation is that you know you are entitled to a certain amount of money, your counterpart is the government so you know they eventually will pay you and all you need is enough money to bridge the gap for a month or two. You would imagine someone who has worked for years should have such a trivial amount of money available - but apparently not.
*) if you loose your job you are entitled to ~62% of your pay capped based on an income of ~68k USD so if your pay was 68k USD or 200k USD you get the same amount.
