What do we learn from "De'agah v'Lev Ish Yashchenah"?
Rashi, from Sotah 42b #1: Yasichenah (he should divert it) from his mind.
Rashi, from Sotah 42b #2: Yasichenah (he should speak about it) with others 1 .
R. Yonah: Worry in the heart makes the walls of the heart bend down. Lev is feminine here; we find "Mah Amulah Libasech" (Yechezkel 16:30).
Malbim: All Midos are hidden in the Nefesh, until the Ru'ach brings an image on the heart. Man can raise the image above, or lower it below. E.g. he can arouse a good or bad image from Midos, and then the Ru'ach reveals it and puts it on the heart, e.g. of pride, humility, envy or desire. Worry is a Midah of the Nefesh, to be concerned for the future. When it rules in the heart, it consumes the Nefesh and the flesh. Also an Ashir and serene person, when worry rules over him, he worries about the future, lest his house be destroyed, or his wealth be depleted, or his sons will die, or enemies will rule over him
Malbim: This means that he should switch the worry for different images that gladden him. Also the other opinion in the Gemara (he should divert it) from his mind is Emes. The two opinions are based on the two parts of the verse.
How does one fulfill "v'Davar Tov Yesamechenah"?
Rashi #1: He engages in Torah; this gladdens the worry in his heart and saves him from it.
Rashi #2: According to the opinion that Yasichenah (he should speak about it) with others, it is good that his friend will console him to gladden the worry.
R. Yonah: Davar Tov is like "Rachash Libi Davar Tov" (Tehilim 45:2). When a person understands a matter of Chachmah, or counsel and Da'as, and it reveals to him the Emes, his heart rejoices. Therefore, if there is worry in his heart, he is wise and looks in Divrei Chachmah. His heart rejoices it is not contemplating them when the eyes of his thoughts are opened, like one delights in his vision - "Me'or Einayim Yesamach Lev" (15:30).
