This quote succinctly captures the holistic nature of training, transcending mere physical exercise to encompass both the body and the spirit. The phrase "tighten up the slack" suggests eliminating inefficiencies or weaknesses—whether in muscle coordination, mental focus, or habits—that can hinder progress. Toughening the body refers to building resilience, strength, and endurance, acknowledging that physical robustness provides a foundation for not only external challenges but internal struggles as well. Yet, the inclusion of "polish the spirit" elevates the purpose of training beyond the corporeal. It implies that through dedicated effort and discipline, the inner self becomes refined, gaining wisdom, patience, and harmony.

Reflecting on this, it becomes clear that true training is an integrated process where improvement is multi-dimensional. Physical conditioning alone is not enough if the spirit remains unbalanced or the mindset under-developed. Similarly, honing mental or spiritual qualities requires the anchor of a strong, disciplined body. This synthesis helps build character—an essential aspect in fields like martial arts and life in general. In a world focused on instant gratification and superficial strength, this quote reminds us that enduring growth involves confronting the entire self, addressing weaknesses, enduring hardship, and nurturing the inner calm. It speaks to the discipline necessary to achieve excellence across multiple dimensions, encouraging continuous self-improvement.

Furthermore, the quote emphasizes intentionality in training—it's not mindless repetition but a purposeful journey toward wholeness. This integrity and balance may ultimately lead not just to improved performances but to a more fulfilled, peaceful existence, aligning with the spirit of Morihei Ueshiba's teachings in "The Art of Peace."