Hatavat chalom is an ancient Jewish dream practice that is still used. If you have a bad dream, or one that worries you for some other reason, then the Talmud recommends hatavat chalom. First you bring together three friends; the Rama, Rabbi Moshe Isserles, specifies that they should be people who like you. (A beth din will also do.) Then you tell them that you had a bad dream, and they respond, "It should be good, and let it be good." Finally, recite a prescribed series of biblical verses whose theme is the reversal of bad fortune.
The practice is based on the Talmud's central assumption about dreams, "All dreams go after the interpretation". They elaborate, "A dream that is not interpreted is like a letter that is not read". The interpretation of the dream is what determines its meaning and potential influence on your life (whether one considers the influence to come from the deep-seated fears and expectations that the dream expresses, or from some mystical mechanism). The ritual of hatavat chalom aims to undo the negative forebodings about the dream and replace them with an optimistic interpretation.