question, how does busting yourself up during practice helping self-defense? maybe that's why they called it self-defense, as in defending against oneself.
the more you risk, the more rewarding is the training, up to a point.
taking hard falls on the mat conditions the body, particularly the crucial neck muscle that support the head, and the vigorous and supple "debate" improves balance and the ability to stay calm and clear minded.
kyokushin (bare knuckle full contact) karate or muay Thai,
judo or jujutsu
are the "three legs" or dimensions of my budo practice, along with daily shikantaza practice.
having fun while improving martial conditioning is the hobby I am committed to. We get what we put into it, risks and all.
aside from the fun times, intrinsically, had by appropriately punishing training, the benefits are clear. For example, I fell off a ledge, of significant height, during cross country mountain bike race training, but landed, with my bike on a good side break fall, able to ride away with mere bruises. Sweet.