A Tibetan story tells of a meditation student who, while
meditating in his room, believed he saw a spider descending
in front of him. Each day the menacing creature returned,
growing larger and larger each time. So frightened was the
student, that he went to his teacher to report his dilemma.
He said he planned to place a knife in his lap during
meditation, so when the spider appeared he would kill it.
The teacher advised him against this plan. Instead, he
suggested, bring a piece of chalk to meditation, and when
the spider appeared, mark an "X" on its belly. Then report
back.
The student returned to his meditation. When the spider
again appeared, he resisted the urge to attack it, and
instead did just what the master suggested. When he later
reported back to the master, the teacher told him to lift up
his shirt and look at his own belly. There was the "X".