I once quit a job five days in, because the boss (on day 4) berated me in a way that indicated a lack of anger control. I gave it a day to think it over, then quit.

I had been hired through an agency, and called them, being apologetic and saying I hoped I hadn't endangered their relationship with their client (although no way I was staying). They said I hadn't, and by the end of the call it became apparent that I wasn't the first person to quit in this way.

One thought exercise you might consider, to see if you are being unreasonable or not. Imagine, as a thought experiment, that you were needing to explain to someone (say at your next job interview) what was wrong with your "insufferable" bosses. If you have a hard time explaining (even as a thought experiment) why your immediate bosses are insufferable, then you would want to introspect a bit more as to what is really bothering you. But, if you are able to explain the problem clearly (and professionally), perhaps to a non-work friend or something, then it's probably not just you being in a bad mood or whatever, and you should start looking.

One additional thing to mention is you can start looking before you quit, just to see what the market currently is like for you.