Chapter Three : Practice 56

The Founding Master addressed the congregation at the opening ceremony for a retreat at a meditation hall,
“Entering an intensive session at a meditation hall is like a patient entering a hospital. When a person’s physical body gets ill, one is treated with medicine at a hospital; when the mind gets ill, one is treated with the Way and its power at a school of religion. Therefore, just as the Buddha may be called the Medicine King, so too can one say that his doctrinal teachings may be called his medicines and his temples his hospitals. However, most people recognize only physical illnesses as sicknesses and spend their time and money to cure them, but do not recognize illnesses of the mind as being sicknesses and do not even think of curing them. How can this not be lamentable to the wise? No matter how severe illnesses of the body may be, their pain will last only a lifetime; or, if they are minor, they can be cured in a short period. But if illnesses of the mind are left untreated, they will become a seed of transgression and suffering interminably throughout the future. If one has illnesses of the mind, one will lose one’s freedom of mind and be attracted by the temptations of external sensory conditions. One will then commit wrong speech, wrong action, and wrong thought, and willingly enter the realm of death, willingly invite contempt from others, and willingly create suffering for oneself. As a result, transgressions will follow from transgressions and suffering from suffering, and there will be no hope of recovery. However, if the mind is free from illnesses, throughout the wide land of the worlds of the ten directions one will readily transcend suffering and happiness, come and go freely, and be able to make use of all blessings and happiness as one pleases. Dear disciples! During this Sŏn-retreat, diagnose well the illnesses of the mind that each of you has and dedicate yourself to curing them.”

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I think the explanation makes complete sense, but I would add that people are not just bodies and minds, they are eternal spirits. People get caught up in their earthly lives, and forget that when they 'end' here, the real 'them' does not end, but goes on. That is why we need to pay more attention to what's going on inside of us, because it is very true, frustration, anger, depression, and all other menacing attitudes and agents, can and do make us 'sick' and thus spread more sickness. If we cared for our inside like we do our outside, we would not be in the shape we are in this world, today.