Well, it didn't occur to me either till I looked back on my little six month log, and saw the pattern. And, thought about how often I sacrifice my mountain of a stack because I played until 3am like an idiot.
I dunno, this might be obvious to some - especially those with experience, and seem like a given - but it wasn't obvious to me till the numbers started talking to me. Then I started thinking about, why could that be - well, the reason for me is I let the intoxicating experience take over and ruin my senses. I don't even realize how tired or mentally lazy I'm getting. Logic gives way to excitement, and bad calls. So now, I always limit to 2hrs, and I gotta say it's been working great the past cpl weeks at the cash games. I look down at my phone and see I've hit the two hour mark, and every time I feel like I'm tearing myself away from the game prematurely, but then I feel really good as I drive home with 2 or 3x my buy-in safely in hand.
I'm getting pretty good at study, memorization, categorization and prediction of player behavior, but it takes a LOT of focus. I can only do that effectively for at most 2 hours or so. Also, after that time, the percentages of
pot odds turn to fuzz in my brain unless it's super easy figures. And I can forget about figuring implied odds.