I worked at a Big 4 firm and promptly quit during the middle of busy season 2 years ago and have not looked back. I was your age when I turned in my pencil. I saw my future, Manager, Director, Partner and I was dreading it more than looking forward to the "prestige". i figured I needed to do something NOW, like my hair was on fire to get out.
There came a point one weekend after weeks upon weeks of coming home and crying, while simultaneous downing a bottle of wine nightly, and working until the wee hours of the morning where I said I CAN'T TAKE IT ANY MORE. I asked myself to think about the companies I really could see myself working at and then binged a whole weekend looking for roles that would match my skill set at these companies. I applied to a lot of places and a lot of jobs and was called back by a large tech firm and got an interview. While I was waiting for an answer on the interview, I made the decision to quit, regardless if I got the tech job or not. This interview with this fancy company gave me the confidence that companies wanted people with my skills and I WOULD find a job. About 1 week into busy season, I pulled the trigger. Luckily, I found out the same day I DID get the job at the big tech company and haven't regretted my decision yet.
I work normal hours, make MORE money (certainly more per hour but just more overall too), work for an awesome place that has fantastic benefits, do cool and interesting things. The greatest gift was getting my TIME and SANITY back. It freed up my mental and emotional self to find MMM and invest in my passion for buying income properties. I spend more time with my family and friends and feel RESTED for the first time in probably years.
All around, the Big 4 experience was a great foundation, but I knew I couldn't be a "lifer". I still know tons of people there, who for one reason or another stay and muscle it out, but I am so much happier than I was 2 years ago, like you, on the brink of another grueling busy season.
Only you can decide if you are comfortable leaving without another gig lined up but if you work in a major metro area, you will likely find something pretty easily with your background at a private company.
I think I need to scream something to reverse the brainwashing I feel we were all subjected to... YOU WILL MAKE GOOD MONEY SOMEWHERE ELSE, YOU WILL DO COOL AND INTERESTING THINGS, YOU WILL HAVE A GREAT CAREER POST BIG 4, THE BIG 4 IS NOT THE END ALL BE ALL, YOU WILL BE OK!!!!
Good luck pulling the rip cord!