Maintaining a State of Joy
The story of Miriam’s leprosy teaches us a great deal about the concept of נבואה, prophecy. We learn how Moshe’s prophecy was on a higher level than that of any other prophet.
The Rambam explained that a prerequisite to receiving prophecy was maintaining a high level of joy. Some prophets would play music to lift their spirits before receiving the word of G-d. Yitzchak asked Eisav to prepare a meal for him to place him in the right frame of mind to give a blessing.
From here we learn how important it is for all of us to maintain a high level of Simcha in serving Hashem. It shows that our Mitzva observance is not a burden. The ארחות צדיקים says that we get a much greater reward when we fulfill the words of the Torah happily.
The חובת הלבבות writes that when one observes Mitzvot with joy, it is an indication that they have true אהבת ה׳, love of G-d.
There is also the story in the Gemara of two men who did not appear to be particularly learned. Yet, they merited a place in עולם הבא. Upon investigation, their special merit was that they made people laugh. This is a reminder that a major part of our worship of Hashem, is to do it in a state of joy.