It is very poor policy to dwell negatively on unpleasant aspects of the past that you know, because some portions of the probable self may still be involved in that past. The concentration can allow greater bleed-through and adverse identification, because that part will be one background that you have in common with any probable selves who sprang from that particular source. To dwell upon the possibility of illness or disaster is equally poor policy, for you set up negative webs of probabilities that need not occur. You can theoretically alter your own past as you have known it, for time is no more something divorced from you than probabilities are. The past existed in multitudinous ways. You only experienced one probable past. By changing this past in your mind, now, in your present, you can change not only its nature but its effect, and not only upon yourself but upon others. Pretend a particular event happened that greatly disturbed you. In your mind imagine it not simply wiped out, but replaced by another event of more beneficial nature. Now this must be done with great vividness and emotional validity, and many times. It is not a self-deception. The event that you choose will automatically be a probable event, which did in fact happen, though it is not the event you chose to perceive in your given probable past. Telepathically, if the process is done correctly, your idea will also affect any people who were connected with the original event, though they can choose to reject as well as accept your version.  Seth (Jane Roberts), “Seth Speaks”, Session 566.