It's paradoxical that "my" body was born prematurely and remained smaller than most others, yet I became aware of the importance of daily physical workouts. I've read many books on the subject by medical professionals as well as trainers and tried various physical workouts until I settled on three: bodyweight muscle training and running (ChiRunning) in the morning, and yoga (Iyengar Yoga) at night.
I continue these three to maintain the strength, stamina, and flexibility of "my" body. I've been asking myself which of the three is the most important though all of them are indispensable. Having continued to read various books by medical professionals, I've become more and more convinced that strength - and hence muscle training - is the most important for aging well.
If you are interested in learning the theory and practice of muscle training, I would highly recommend Forever Strong by Gabrielle Lyon and You Are Your Own Gym by Mark Lauren respectively. Of course, you are also more than welcome to contact me by email!
I've even become an "evangelist" of muscle training in general and bodyweight muscle training in particular, especially after seeing why a number of older people fall and become bedridden. The "gospel" I've started to share with others is fairly simple: Use them or lose them, but it's never too late to start using them again, or even for the first time. This can also be called the "gospel" of neuroplasticity.
I've also noticed that many people seem to have to change their mindset before they can start training their muscles. The two biggest mental obstacles I've identified so far are inertia and lack of self-discipline. I can't say that I myself had to cope with either of them in the beginning. But they, too, can be "rewired." Neuroplasticity applies to both the body and the mind.
As far as I'm concerned, what makes my daily "ritual" of three physical workouts, especially bodyweight muscle training, even "sacred" is, paradoxically, the awareness that I'm only borrowing this physical body so that the soul may accomplish its mission in this physical world. From this perspective, training "my" body is not a pastime but an obligation, just as I feel obliged to return a book I borrow from a public library in the best possible condition.