Halakha Amsal 15:15: Mishneh Torah, Human Dispositions & Shulchan Arukh, Orach Chayim

The straight path is the mean disposition found in each and every tendency of all the human tendencies. Such tendency is removed from both extremes an equal distance, and is not nearer to one than to the other. Therefore have the wise men of yore commanded that man should ever review his tendencies,¹Sotah, 5b. C. estimate them, and direct them toward the middle-path so that he will be sound in body. How may one do it? He should not be an excitable person, easily angered; nor like the dead without feelings, but adopt a middle-course, not to become indignant, save only at something big which is worthy enough to be angry at, so that the like should not be done another time. Likewise shall he not crave for aught save the things which the body requires, and without which it is impossible to be, as the subject is spoken of: "The righteous eateth to the satisfying of his soul" (Pro. 13.25). Likewise shall he not continue to fatigue himself in his affairs, save to acquire what is necessary for him to live on for the time being as the subject is mentioned, saying: "A little that a righteous man hath is better" (Ps. 37.16). He should not be too close-fisted, nor yet squander his money, but give Z'dakah within the means of his hand, and lend accordingly to the needy. He should not be too optimistic and playful, nor too pessimistic and mournful, but spend all of his days in good cheer and with a pleasant countenance. So should he measure all the rest of his tendencies. And this path is the path of the wise men. Every man whose tendencies are mean tendencies of the middle-course, is called wise.

One does not say Tachanun on the 14th and 15th of Adar I, and the law of fasting and eulogizing on those days. Containing one paragraph.
On the 14th and the 15th day of Adar I, we do not fall upon our faces [recite Tahanun], and we do not say [Psalm 20] "A Psalm... may the Lord answer you," and on those [days], it is forbidden to eulogize or to fast. There are those who say that even eulogy and fasting are permitted. Rema: The custom is according to the first understanding. There are those who say that one is obligated to increase in joy and feasting on the 14th of Adar I (Tur in the name of the Rif); however, this is not our practice. Nevertheless, one should increase their feasting slightly, in order to fulfill the opinion of those who are stringent (Hagahot Maimuni in the name of the SeMaK). "But the good-hearted has a continual feast" (Proverbs 15:15).