So much can be said about humor and its value not just to comedic writing, but to ALL writing.
Wilbers says it this way, "...to tell a joke is to declare your humanity... To appeal to another person's sense of humor is to affirm a common bond."1 And, "Humor reduces the distance between writer and reader (and between speaker and listener)."2
Even the writer of drama should employ a bit of humor here and there, not only to give the reader or audience a break, but to offer insights about the realities of life that can best be understand through comedy. Maybe kind of like, 'I can either laugh or cry, and laughing's more fun,' when faced with difficulties in our lives.
In chapter 50 of Mastering the Craft, ten types (tropes) of humor are discussed. You're probably already using many of them without realizing it... paradox, situational irony, sarcasm, overstatement, wit...pick something new and try it in your current manuscript!
Mastering the Craft, p 278
Mastering the Craft, p 279