“Just as a border city is well-guarded within and without, even so should you guard and protect your mind. Do not let this opportune moment slip away.”
Canonical Pali Original: Nagaraṃ yathā paccantaṃ, guttaṃ santarabāhiraṃ; Evaṃ gopetha attānaṃ, khaṇo vo mā upaccagā.
— Gautam Buddha
The Awakened One, Founder of Dhamma
Pali Canon: Dhammapada 22.315 emphasizing constant self-guarding and taking advantage of the rare opportunity of conscious human existence.