No matter who you are, there are always going to be times where you have to be aware of your own self-preservation. For some, it will be something you have to deal with more often than others. Perhaps you're a smaller guy, or a woman, or a bit older...but even a big, strong guy coming back from an injury. or getting ready for a tournament and you're pushing extra hard and you're extra tired (which can make you more prone to injury)...there will be times where you have to become aware of your own self preservation or risk injury.
Sometimes it can be a struggle with your ego. You're caught in a bad position and you're fighting it and you get to the point where you have to decide: do I tap and go again or does the ego tell me I'm okay, I can go farther and I don't tap, get injured and sit out for two weeks.
Sometimes self preservation means not rolling with certain people.
There are many different types of people that come in to train. For me, sometimes self preservation can mean that I don't roll/break in the newbie 220lb. white belt. It's not his fault. He's a big guy just starting in the sport so he probably doesn't have the control (over his body and/or ego) to roll with a small female.
There's the guy who always goes 110 percent. He can be a great training partner if someone's getting ready to compete or do mma, but maybe not for someone coming back from an injury.
Maybe you've had an extra exhausting day and you haven't had a good night's sleep in several days so you're not quite "on"...maybe you take it a bit easier and are a little more careful about who you roll with.
How long do you see yourself doing the sport? Keep in mind the larger picture, your safety and longevity. Jiu-jitsu is not about one roll. It's not about one training session. Jiu-jitsu is a tough sport. There are no kata's. Injuries WILL happen. That is inevitable. So, how do you continue to train and last in such a tough sport? Trying to minimize unnecessary injuries can help.