Most I've made in a single day would be my $800 I took from a $1/$2 NL cash game in just over two hours (I was newly 17 at the time)
Most I've ever lost in a single day was $10.
I've only done one real cash game, and that was mentioned above. I probably played like a donk compared to them, but I had great cards and some huge pots that night, never dropped under my $100 buy in, and I doubled up in one hand after about 20 minutes.
The only reason I've never lost more than ten is simply because I put myself on a $10 a week limit (because I've not actually built a
bankroll yet) to keep myself in check, and 99% of the time I play it's $5 home games with a few buddies.