I think about this a lot and it's one of the reasons I'm here on this forum.
I'll skip all the explanation and just say that my opinion is that chivalry in our modern sense of the word, has never really been a cultural norm in any western culture. The idea was highly romanticized in the 19th century, along with nearly everything else about medieval times, and that has unfortunately stuck because medieval studies has never been important to the majority of human beings since the medieval era. So we who find such things interesting must discover what the real meanings are for ourselves. As for me, my obsessive curiosity led me on a journey of discovery that has more or less ended up giving me mixed feelings on the subject. As it turns out, not only were real knights not all that chivalrous, even the ones who were would never fit our modern definition of what chivalry is. A great man revered by millions as a paragon of virtue was also one who had put to death every man, woman and child of a village that defected to their enemy. Surviving stories have been intentionally embellished to make people look better (or in some cases worse) than they really were. The mere idea of chivalry in medieval times only applied to the upper social classes - "defend the helpless" meant women and children of knights and nobles, not every helpless person.
What all this means to me is that if I want to feel like I am living up to my own ideals of behavior, only I can be the judge of my success. What chivalry means to everyone is irrelevant - it only matters what it means to me, because in the end whether I've lived up to "everyones" expectations won't be important. But it can be said there is one thing analagous with my medieval idealized knight persona and myself: my conscience must be my guide, and the same is true of every other man. I cannot control what others do, or what others think of me. I can only control my own actions, and attempt to live up to my own standards, and be content with myself or not based on that.
And perhaps most ironically of all, in all likelihood that is exactly what those unchivalrous, murdering, virtue paragon real knights of medieval times were thinking to themselves all those centuries ago.
As for myself, what I do is I usually look for opportunities to live up to my standards when it will really matter. I ask myself "Am I doing the right thing?" And if I fail that test, "What will I be able to live with tomorrow?"
Scott