The matter can be put in another way. The pleasures and frustrations, the happiness and suffering experienced by each individual are the inevitable fruits of beneficial and evil actions he has perpetrated, thus adding to his store. If at a particular moment in this present life the fruits of a person's good actions ripen he will recognize, if he is a wise man, that they are the fruits of (past) meritorious deeds. This will gratify him and encourage him to achieve more merits. Similarly, when a person happens to experience pain and dissatisfaction, he will be able to bear them calmly if he maintains an unshakable conviction that, whether he wishes it or not, he must suffer and bear the consequences of his own (past) deeds, notwithstanding the fact that normally he will often find the intensity and extent of his frustration hard to bear. Besides, the realization that they are nothing but the fruits of unskilled action in the past will make him wise enough to desist from unskilled deeds henceforth. Likewise, the satisfying thought that, with the ripening of past (evil) karma, a certain part of the evil fruit accrued by former unskilled action has been worked off will be a source of immense relief to him.
A proper appreciation of this wisdom will contribute to grasping the essentials for achieving peace of mind and body. For instance, suppose a person is suddenly afflicted with critical physical suffering due to certain external factors. If, by the force of sheer will power (based on the conviction that he is himself responsible for his present misery and sufferings), he can neutralize the extent of his suffering then his mind will be much comforted and at peace.
Now let me explain this at a rather higher level. This concerns the strivings and efforts that can be made for the systematic destruction of dissatisfaction and its causes.
As stated before, pleasure and pain, happiness and dissatisfaction are the effects of one's own good and bad, skilled and unskilled actions. Skillful and unskillful (karmic) actions are not external phenomena. They belong essentially to the realm of mind. Making strenuous efforts to build up every possible kind of skillful karma and to put every vestige of unskillful karma away from us is the path to creating happiness and avoiding the creation of pain and suffering. For it is inevitable that a happy result follows a skillful cause and that the consequence of building up unskillful causes is suffering.
Therefore, it is of the utmost importance that we strive by every possible means to increase the quality and quantity of skillful actions and to make a corresponding paring down of our unskillful actions.
How is this to be accomplished? Meritorious and unmeritorious causes which result in pleasure and pain do not resemble external objects. For instance, in the human bodily system different parts such as lungs, heart and other organs can be replaced with new ones. But this is not so in the case of karmic actions, which are purely of the mind. The earning of fresh merits and the eradicating of bad causes are purely mental processes. They cannot be achieved with outside help of any kind. The only way to accomplish them is by controlling and disciplining the hitherto untamed mind. For this, we require a fuller comprehension of the element called mind.
Through the gates of the five sense organs a being sees, hears, smells, tastes and comes into contact with a host of external forms, objects and impressions. Let the form, sound, smell, taste, touch and mental events which are the relations of the six senses be shut off. When this is done the recollection of past events on which the mind tends to dwell will be completely discontinued and the flow of memory cut off. Similarly, plans for the future and contemplation of future action must not be allowed to arise. It is necessary to create a space in place of all such processes of thought if one is to empty the mind of all such processes of thought. Freed from all these processes there will remain a pure, clean, distinct and quiescent mind. Now let us examine what sort of characteristics constitute the mind when it has attained this stage. We surely do possess some thing called mind, but how are we to recognize its existence? The real and essential mind is what is to be found when the entire load of gross obstructions and aberrations (i.e. sense impressions, memories, etc.) has been cleared away. Discerning this aspect of real mind, we shall discover that, unlike external objects, its true nature is devoid of form or color; nor can we find my basis of truth for such false and deceptive notions as that mind originated from this or that, or that it will move from here to there, or that it is located in such-and-such a place. When it comes into contact with no object mind is like a vast, boundless void, or like a serene, illimitable ocean. When it encounters an object it at once has cognizance of it, like a mirror instantly reflecting a person who stands in front of it. The true nature of mind consists not only in taking clear cognizance of the object but also in communicating a concrete experience of that object to the one experiencing it.[*] Normally, our forms of sense cognition, such as eye-consciousness, ear-consciousness, etc., perform their functions on external phenomena in a manner involving gross distortion. Knowledge resulting from sense cognition, being based on gross external phenomena, is also of a gross nature. When this type of gross stimulation is shut out, and when concrete experiences and clear cognizance arise from within, mind assumes the characteristics of infinite void similar to the infinitude of space. But this void is not to be taken as the true nature of mind. We have become so habituated to consciousness of the form and color of gross objects that, when we make concentrated introspection into the nature of mind, it is, as I have said, found to be a vast, limitless void free from any gross obscurity or other hindrances. Nevertheless, this does not mean that we have discerned the subtle, true nature of the mind. What has been explained above concerns the state of mind in relation to the concrete experience and clear cognizance by the mind which are its function, but it describes only the relative nature of mind.
[*]
These two aspects, 'taking cognition' and 'communicating experience' refer to knowing what the object is and how it feels, tastes, looks, etc.