Eventually (if we live long enough!), we will all get old.
No matter what physical shape we are in right now, the skills, attitudes, and behaviors we are building right now will either help us or hurt us during the very predictable future times when our physical selves aren’t as robust as they once were.
We should therefore work, right now, to get self defense skills that can hold up across a wide variety of physical abilities. We should also look for instructors who understand that not everyone is in great physical shape, and who give their students strategies that will work well even for people who are not especially strong, athletic, or physically fit.
No matter what our physical skill level right now, we can work to improve it. And we should!
But also, no matter what our physical skill level right now, we will likely be worse off at some time in the future. Whether that is the simple process of aging, or something more dire such as getting injured in the middle of a criminal encounter, we will likely need defense skills that work even for people who are not strong and fit. We should plan for that.
Sometimes we just need to be able to play the cards we’re dealt.