I study kenjutsu (and aikido) - and have friends/colleagues who are also serious kendo practitioners. Kendo has pluses and minuses - the shinai used can teach

I study kenjutsu (and aikido) - and have friends/colleagues who are also serious kendo practitioners. Kendo has pluses and minuses - the shinai used can teach habits of "flicking wrists" which just don't work with heavier weapons. And yet advanced practitioners have serious focus and skills. I much admire a female Japanese friend (and sempai) who was told by our sensei to go and study kendo (while not slacking off in her other studies). In her fifties, and a 5th dan, off she went and started from scratch but made rapid progress, and brought back what she had learned. Our sensei told other people to do different things - horses for courses. But what does it mean "to fight"? No rules? For your life? For someone else's life? These are the fundamental questions to be examined and resolved. How would you know if you are ready?