Being expendable: Biglaw attrition rates at the largest firm can hover around 20%. Know what that means about you? No leverage from day one until the day your two weeks notice lands. There is 0 incentive for anybody to make the job compatible with life. There is a line of people waiting to replace you. Until something actually breaks or goes wrong, how tired you are is directly proportionate to how much money the partners are earning.
The internal prison: When you're overwhelmed in biglaw, work/life balance quickly becomes "do a good job / life" balance. If the deadline looms and there's nobody else to do the work, the only options are do a mediocre job while getting sleep/life -- or making it sparkle while bleeding for it. There's something uniquely toxic about crushing yourself, but biglaw attracts the kind of people who do it. It makes the work product better, generates hours and is just baked into the system.
Billing and time keeping: Long day at the office? DOCUMENT EVERY 6 MINUTE INTERVAL OF IT UNTIL YOU GO HOME. Too tired? Good luck remembering it all tomorrow! Running timers? ETERNAL GUILT IF YOU PEE OR TLS WITHOUT PAUSING THEM. Had a day with a lot of down time? ENJOY THE PANG OF FEAR/GUILT AS YOU ENTER YOUR "SLOW" day.
Gnawing sense of inadequacy: I thought this was unique to being a 1L or a law student, but it turns out it just runs in the profession. The difference between "gnawing sense of inadequacy" and "
imposter syndrome" is the constant proof that you are, in fact, an imposter. Red markups, dirty looks, obvious failures. Biglaw tasks/deadlines are frequently impossible (like, flat out incompatible with the law of physics) and the humble hammer will fall repeatedly on your forehead. As far as I can tell the only time it stops is when you decide to accept "victory" on days that you shit the bed less frequently, or less disastrously, than your peers.