Don't check your net worth several times a day? ;-)
It strikes me that the problem here is your thinking: it sounds like you want your account to be a certain dollar amount on a certain date, at which point you will have permission to quit, and so you are anxiously watching the account go up and down to figure out the likelihood of that happening. And that, of course, is yes!-no!-yes!-no!-yes! anxiety-producing.
So I would suggest moving away from the all-or-nothing thinking and start making plans for different alternatives. What happens if the market crashes a week before you quit? What happens if it crashes a week after you quit (because, of course, volatility doesn't go away just because your job does)? What if future returns are lower than you are projecting? Usually the answers to these questions aren't "well, I have to work until I'm 70, then, dammit" -- it's, well, I can cut some optional expenses, or I can get a part-time job, or I can try to monetize my hobby, or whatever. IOW, I bet you in most of those scenarios, you can still find a way to quit your current job and make it work long-term. Which means that the market hitting XYZ as of [date] is not the be-all, end-all of your existence, and isn't worth so much of your mental attention.
Of course, you could run the various scenarios and then decide that you'd rather just work another X months/years so that you can be confident that you can FIRE on your original budget. But I can tell you from personal experience that a job feels completely different when you know you no longer need it and are instead choosing to work there for other reasons. And if it doesnt, well, quitting is always an available option.
And finally, if you go through all of the exercises and there is no way you can make a reasonable alternative work on your planned budget, maybe your budget is too tight, and/or your risk tolerance is lower than you anticipated -- in which case you should re-evaluate your underlying assumptions. Because the market is going to go down after you FIRE, and there will be [multiple] recessions over the next 40-50 years; the only questions are "when?" and "how bad?" So you need to feel confident that your plan -- including your various backup options -- will see you through that.