Winning limits aren't really the best idea. Stop losses are better. Sure Ferguson preached the idea of leaving a table when the amount in your stack represents 10% or more of your total roll , but this concept doesn't mean you "leave" the session or game, you might just rebuy full at another table or take a break and come back at the initial buy in.
Sure variance can leave you scratching your head wondering where your 3x BI stack went after a guy with 4x your stack calls from behind and gets a 1 outer on river to get quads against your flopped boat but long term we want these spots.
One thing I've noticed as I continue to focus on mental game theory as well as discipline and attention to focus and concentration is that I naturally start to "check" where I'm at on the tables after a bit of playing. I don't say "well I'm up 2BIs overall time to leave" rather I say "let's take a moment to see how I'm feeling. Do I need a break, have a made a few mistakes in the past few hands, does this mean I'm fatigued? Did I get stacked just now and then in another hand make a big error or feel tilted? " So basically if I conclude that I now feel tired, need a break, or something changed in my focus and concentration where I'm not making the best decisions and focusing on the current hand only, I may leave the table. I've found now I almost always automatically leave a table if I drop more than 2 BIs and usually if I find myself struggling across multiple tables and and am down more 3BIs or more it seems to match up with a feeling of being fatigued and not playing optimal poker, thus time for a break or stop for the day even.
Basically sometimes I leave up, sometimes I leave down. I try to leave up but as soon as I begin to consider leaving the table I must ask myself why. Usually it's fatigue impacting level of play which means it's a good idea to leave.
There's other variables to consider too of course. I mean if I'm at a 6max game with 3x the BI why leave? I'm doing well and it's ok to lose a little profit in the pursuit of more profit with sound decisions. I mean I'd rather be up at a table and playing with that profit than down at a table and having to keep monitoring for the creeping in feeling of "needing to get even again." Also if the table changes, players leave or whatever, then I might leave.
Overall my point is to consider leaving based on either a stop loss OR on how you feel in your current mental state when playing. If any time something changes: fatigue, tilt, lack of focus, stuck thinking about a prior hand, too much focus on a certain dollar amount, it's time to consider leaving the table if you can't get refocused.
Sure we all want to see our number rise and lock in that "profit." But remember the next time you sit down you could win a ton or lose a ton (which situation do you want to set a stop limit to?) so "locking in a win" really does nothing long term for profits , it might feel good, but it doesn't reflect your abilities OR your true earnings long term. Case in point: in my current challenge I went on a nice heater across a few sessions. Then in one day promptly lost 6BIs of that. Took a break, next two days recovered most of it back. Yeah it would've been nice to keep seeing the BR go up and up, but I'd rather play good poker and see it go up and down and look at my roll and know I'm well rolled now and safely minimizing risks of going busto. It's a lot easier to dig out of a downswing I think when you have the
bankroll management and discipline down (keep enough BIs in the roll, set stop losses, keep attuned to your emotional and mental state during play) then if you just keep leaving whenever up, you're not preparing yourself game wise or mentally for the inevitable losing sessions which are just part of poker. Do everything right and still lose, it's going to happen. You need to feel that experience of being up X amount of BIs, getting the money in good when playing good and then having it all sucked away in one hand by some guy with 102o rivering a 1 outer. If you have the discipline and focus, you'll be mad but will get over it, not let it tilt you, and not feel like you need to run every time you're up a few bucks for fear of losing that profit short term.