The thought of affection takes a definite form, which it builds out of the matter of the thinker's mental body.

Because of the emotion involved, it draws round it also matter of his astral body, and thus we have an astromental form which leaps out of the body in which it has been generated, and moves through space towards the object of the feeling of affection.

If the thought is sufficiently strong, distance makes absolutely no difference to it; but the thought of an ordinary person is usually weak and diffused, and is therefore not effective outside a limited area.
When this thought-form reaches its object it discharges itself into his astral and mental bodies, communicating to them its own rate of vibration.
Putting this in another way, a thought of love sent from one person to another involves the actual transference of a certain amount both of force and of matter from the sender to the recipient, and its effect upon the recipient is to arouse the feeling of affection in him, and slightly but permanently to increase his power of loving.

But such a thought also strengthens the power of affection in the thinker, and therefore it does good simultaneously to both.
Every thought builds a form; if the thought be directed to another person it travels to him; if it be distinctly selfish it remains in the immediate neighbourhood of the thinker; if it belongs to neither of these categories it floats for awhile in space and then slowly disintegrates.

Every man therefore is leaving behind him wherever he goes a trail of thought forms; as we go along the street we are walking all the time amidst a sea of other men's thoughts.