The white bear effect originated from an experiment by Daniel Wegener, a social psychologist at Harvard University in the United States. He asked participants to try not to imagine a white bear. As a result, the participants' thinking rebounded strongly, which quickly surfaced in their minds. The experimental results confirm that when we deliberately divert attention, and our thinking also begins to appear unconsciously self-surveillance behavior--monitoring whether we are still thinking about things we shouldn't think about
People who are broken in love try to forget their former lover,  but only to find that the image of the other person becomes clearer in their minds.
that we can't give up our attention to things fundamentally.