emphasizing the brain-impression.

A little pain is made a big one by persistent dwelling upon it; what
might have been a short pain is sometimes lengthened for a lifetime.
Similarly, an old pain is brought back by recalling a
brain-impression.

The law of association is well known. We all know how familiar
places and happenings will recall old feelings; we can realize this
at any time by mentally reviving the association. By dwelling on the
pain we had yesterday we are encouraging it to return to-morrow. By
emphasizing the impression of an annoyance of to-day we are making
it possible to suffer beyond expression from annoyances to come; and
the annoyances, the pains, the disagreeable feelings will find their
old brain-grooves with remarkable rapidity when given the ghost of a
chance.

I have known more than one case where a woman kept herself ill by
the constant repetition, to others and to herself, of a nervous
shock. A woman who had once been frightened by burglars refused to
sleep for fear of being awakened by more burglars, thus increasing
her impression of fear; and of course, if she slept at all, she was
liable at any time to wake with a nervous start. The process of
working herself into nervous prostration through this constant,
useless repetition was not slow.

The fixed impressions of preconceived ideas in any direction are
strangely in the way of real freedom. It is difficult to catch new
harmonies with old ones ringing in our ears; still more difficult
when we persist in listening at the same time to discords.