[Be-Ahavah U-Be-Emunah - Vayakel-Pekudei 5770 – translated by R. Blumberg]

Question: People have all sorts of dreams, good, bad, and strange. Do dreams have spiritual significance, or are they meaningless? And even if they do have meaning, is it healthy to pay attention to them?
Answer: Our Master Rabbi Avraham Yitzchak Kook wrote that the Torah distances us from delving into all sorts of unclear visions, and that it forbids Ov, Yidoni, inquiring of the dead, and all sorts of sorcery. Instead, it instructs us to live with the living. The only exception is dreams. The Torah instructs us to relate to dreams during our lives, and it also teaches us that dreams can be significant, just as nature has its own laws (Igeret HaRe’eiyah, Igeret 79). Surely we see from the Torah that there was truth to the dreams of Yosef, Pharaoh, and Nebuchadnezzar. Likewise, regarding bad dreams, the rabbis enacted personal fast days, as well as the “Hatavat Chalom” ceremony for improving a dream’s outcome, and special prayers to be recited during the Priestly Blessings.
Yet all that applied to earlier times.
In recent generations, the great halachic luminaries greatly decreased their interest in dreams (see the Mishnah Berurah 220:1, and the sources I bring later). And also regarding dreams, about which it is written that we should fast for them even on the Sabbath (Orach Chaim 288:5), recent luminaries said not to fast for them on weekdays, not to hold the "Hatavat Chalom" (improving a dream) ceremony, and even not to recite the special prayer during the Priestly blessing. In this regard the Chazon Ish wrote:
“Many times I had such dreams, and I paid them no mind. It is proper to recite the Ribono Shel Olam prayer about dreams during the Priestly Blessing.” (Igrot Chazon Ish 2:149) The reason is that they decided that these are the sort of dreams that our sages determined to lack meaning, as they only reflect one’s own thoughts (Berachot 55b). As Daniel wrote (Daniel 2:29), “Your thoughts came while on your bed.”
For example, Mishnah Berurah writes that a bad dream after a fast day should not arouse worry since it is the result of the affliction from the fast day, and the same applies to any dream that follows great pain (Orach Chaim 220, Sha’arei HaTziyun 1).
Likewise, if someone dreams that his teeth fell out, if he suffers from toothaches he should not worry (Orach Chaim 288, M.B. 18). The same applies if he worried about something by day and then dreamt about it by night (ibid., M.B. 7).
Kaf HaChaim wrote similarly regarding someone who dreams about the end of Yom Kippur during the days leading up to Yom Kippur (Kaf HaChaim 17). And, Rabbi Yitzchak Abarbanel wrote the same about the bad dreams of people who are not in the best of health (Parashat Miketz).
Today, life has changed greatly from former times, which were more tranquil. Most people lived in villages or small towns, far from the urban crowds, and they were less exposed to earthshaking news.
Today, however, people are bombarded with information day and night from all the media, and they hear about all sorts of terrible happenings. Someone won’t necessarily dream about such things the day after they occur, but such news is stored away in the subconscious, and it bursts forth as dreams from time to time. To the extent that the news is worrisome, it results in nightmares (Piskei Teshuva, ibid.).
Aruch Ha-Shulchan wrote that when people are absorbed with the vanities of this world, those matters find expression in their dreams, especially if they eat a lot before bedtime. Then the digestion process influences the imagination, and such dreams are not real, and they have no meaning (Aruch Ha-Shulchan, Orach Chaim 210:1).
Therefore, one should not worry about his dreams at all. He need not fast over them, and he should further take into account that fasting weakens one’s ability to serve G-d, and sometimes causes anger and nervousness (ibid., 13).
If someone is greatly disturbed by a dream all the same, he can perform a "Hatavat Chalom" ceremony before three friends, or recite the special prayer during the Priestly Blessing. By the way, even in former times, "Hatavat Chalom" was only for people who were distraught over a dream (Orach Chaim 220:1). Certainly the best thing is to learn Torah and give charity, and if one repents, all will be well for him.