(..) This question is one that only a very old man asks. Does this path have a heart? All paths are the same: they lead nowhere. They are paths going through the bush, or into the bush. In my own life I could say I have traversed long long paths, but I am not anywhere. Does this path have a heart? If it does, the path is good; if it doesn't, it is of no use. Both paths lead nowhere; but one has a heart, the other doesn't. One makes for a joyful journey; as long as you follow it, you are one with it. The other will make you curse your life. One makes you strong; the other weakens you.

Before you embark on any path ask the question: Does this path have a heart? If the answer is no, you will know it, and then you must choose another path. The trouble is nobody asks the question; and when a man finally realizes that he has taken a path without a heart, the path is ready to kill him. At that point very few men can stop to deliberate, and leave the path. A path without a heart is never enjoyable. You have to work hard even to take it. On the other hand, a path with heart is easy; it does not make you work at liking it.

(Carlos Castaneda "The Teachings of Don Juan: A Yaqui Way of Knowledge")