(I received this in an e-newsletter from Chabad.org. I share it as an excellent example of Kabbalistic/Hasidic teaching):
THE ILL MAN HEALS THE HERB
(from Ner Yisrael by Rabbi Yisrael Friedman of Ruzhin) 
“This is the law when two men fight and one hits the other with a stone or with his fist: If the victim doesn’t die, but only becomes bedridden, and later gets up and walks under his own power, then the one who struck him shall be held blameless. Still, he must pay for the victim’s loss of work, and he [the sick man] must provide for his [its] complete cure.” (Exodus 21:18–19) . . . the sick man would provide a cure for the herb [reading “his” as “its,” which can be done in Hebrew].
Every Shabbat, Rav Shalom Yosef, who became rebbe after the passing of his father, Rav Yisrael of Ruzhin, would have an elder chassid retell some of the wisdom of Rav Baruch of Mezhibuzh, the grandson of the Baal Shem Tov. Once he was told in the name of Rav Baruch’l (as he was called) an explanation of the verse, “. . . he must provide a complete cure [in Hebrew, v’rapo yerapei)”. He said that the (medicinal) herb would provide a cure for the sick man, and the sick man would provide a cure for the herb. Rav Shalom Yosef explained:
“When G‑d decrees that a man must undergo suffering, the sufferings are enjoined to strike him at a particular time, and to cease at a particular time by way of a particular person and in response to a particular cure.” (Talmud, Avoda Zarah 55a)
Why are a person’s sufferings decreed to occur in a particular way? It is all for the sake of the herb that has to find its tikkun (rectification) by healing the man. When Adam fell from his lofty spiritual level as a result of eating from the Tree of Knowledge, many sparks were toppled and fell below. Every act of eating or drinking serves to restore these sparks to the place where they belong, and thus to bring the world ever closer to perfection.
But how can an herb which is bitter and poisonous find its tikkun? When it is the appropriate cure for a certain ill man, and he takes it with the proper intentions. Then the tikkun is effected and the herb is redeemed. That is what the sages meant, “by way a of particular person”—referring to the sick person. As Rav Baruch’l said, “the ill man heals the herb.”
Similarly, the Baal Shem Tov once explained the nature of divine providence and the way in which fallen holy sparks are returned to their Source: These people are not traveling for the purpose they think. They are actually on a mission from G‑d . . .
“People will travel halfway around the world in pursuit of wealth. The more they endeavor, the more it seems to them that they are indeed acquiring the wealth they desire. But, in truth, it doesn’t work like that.
“These people are not traveling for the purpose they think. They are actually on a mission from G‑d, and on the way to fulfill His will—even if they don’t know it. They are making rectifications in G‑d’s world, and all of their travels and efforts are only for this purpose.
“It is possible that a man could travel to some distant land simply to make a meal of a particular loaf of bread, or to slake his thirst from a certain jug of water that he needs for the tikkun of his soul. The bread may be in one country and he in another, but he must partake of it. Or perhaps he needs to take a sip of water from a particular place, and drink it with a certain intent . . . all this is known only to the Creator. Therefore a man might have to travel thousands or even tens of thousands of miles, to complete in himself that which is not yet whole.
“It also occurs that a person will take an attendant with him on one of his journeys, and in reality the whole trip is only for the purpose of the attendant being able to partake of a particular slice of bread or a sip of the water from a certain place. In reality, the master doesn’t need to make the trip at all, but the attendant does. Since the attendant might be a poor man without the funds to make the trip, G‑d sends the master on business, and he takes the attendant along.”
[I once attended a Kabbalat Shabbat service on a dock over a body of water. It was the summertime. I found it so beautiful, that I began wondering how to reflect that natural beauty in the service. I know a few American and British foksongs, but the only “sea” song I could think of on short notice was “High Barbary” — a song about mercilessly sinking a pirate ship and drowning the pirates. Still, I liked the melody. So, I mentally set “Adon Olam” to it. Creatively re-cycling melodies is nothing new. It was certainly a big part of the “folk revival” era that influenced me so deeply. But I said to the rabbi afterwards, “Some people would say that I adapted the old melody. But maybe Ha-Shem originally intended that this melody be used for “Adon Olam,” and, because of the “Sh’virat ha-Keilim” (the shattering of the vessels), it became used for a song about drowning pirates. In that case, I was performing a “tikkun” for this melody, and putting it back in its rightful, Divinely intended place! What’s more, according to the Rhyzhiner, it was foreordained that it be done, on that night, by me!]
Each thing you do, no matter how mundane, helps recreate the world as it is Divinely intended to be.
 first published by Rabbi Binyomin Adilman in B’Ohalei Hatzadikim; (comments on parshah) Mishpatim; 5760
Rabbi Yisrael Friedmann of Ruzhin [1797 – 3 Cheshvan 1850] was a great-grandson of the Maggid of Mezritch. At a young age, he was already a charismatic leader with a large following of chassidim. Greatly respected by the other rebbes and Jewish leaders of his generation, he was – and still is – referred to as “The Holy Rhyzhiner.” Six of his sons established Chassidic dynasties, several of which – Sadigora, Chortkov, etc. – are still thriving today.
Rabbi Binyomin Adilman is the former head of the Nishmas Chayim Yeshiva in Jerusalem. Back issues of his weekly parsha sheet B’Ohalei Tzadikim, from which this article was taken, may be found on http://www.nishmas.org/