(Sammyundead/Flickr)
The "counterpart sign" (patibagha nimitta) is literally an inner light produced by prolonged attention in meditation. "Where attention goes energy flows" has become a popular slogan of the Law of Attraction movement. Nowhere is it more evident than during sitting practice.We can worry ourselves sick by focusing on stimuli (thoughts, memories, ideas) that produces alarm. We can lull ourselves into fantasy by reflecting on the pleasant aspects of something. But the way of mindfulness is to take things just as they are without evaluating, judging, or resisting them.
Dispassionate observation leads to detachment and liberation, a temporary release of the heart from the burdens it takes as its own the rest of the time.
Gently, non-judgmentally, serenely bringing the mind back to the meditation object again and again as many times as it wanders will eventually produce a meditation sign. Whether using the breath or a candle flame, an image of the Buddha or a photo (perhaps of oneself) to project loving-kindness (metta) towards are all suitable.
Why does the light not come, and what can be done to invite and encourage it?
First, it is necessary to establish oneself in VIRTUE (five or more precepts) so that the mind/heart are free from reproach. One neither has cause to worry about or regret what one has done or left undone.
Second, it is necessary to focus, collect, and CONCENTRATE the mind on a single object. This means purposely excluding all distractions and other concerns. This is when the light comes as a side effect of purification.
Third, the light itself is not important. But with it one is able to cultivate liberating insight called WISDOM. This is done by applying the mind on four "foundations."