On the Four Immeasurable Sublime Attitudes
Mettā: Develop thoughts of love and good will, hoping for your own happiness and that of others. This is like a fortress wall or a cardinal point.
Karuṇā: Develop thoughts of compassion toward yourself and others, aiming at helping yourself and others gain release from all forms of suffering and pain. This is another wall or cardinal point.
Muditā: Develop thoughts of appreciation, taking delight in the happiness you experience and in that experienced by others. This is another fortress wall or cardinal point.
Upekkhā: Develop equanimity, keeping your mind unruffled when your activities or those of others fail or lead to trouble in ways that are beyond your power to help. Keep watch over your mind to prevent it from being upset or defiled in any way. This doesn’t mean being cold or hard-hearted. If you can be of help, you should offer what help you can. Develop equanimity only in those cases that are beyond help.
For these sublime attitudes to be fully developed, they must pervade your thoughts, words, and deeds. Only then will they be effective. Good will expressed in your deeds is like a wall one league thick; good will expressed in your words is still another league; good will expressed in your thoughts is still another league: altogether, three leagues thick. With compassion another three leagues, appreciation another three, and equanimity still another, you have a wall twelve leagues thick. When your thoughts, words, and deeds are protected on all sides in this manner, what do you have to fear?
This, of course, is simply an analogy. If you actually develop these qualities within yourself, you will see for yourself exactly how valuable they are. When your heart is free from fear, it will be able to reach concentration quickly and easily.