Trust
Trust yourself and follow your characters. If you have strong characters, they will speak to you. Listen to them.
If you don’t listen to them — to their inner thoughts, to the subconscious that drives them and that even they cannot knowingly heed — then you fill their lives with something less than a truthful portrayal, and then you are writing melodrama.
It’s hard to listen. It’s easier to talk. The same goes for playwriting. It’s easier to be wilfull and stuff words where they don’t belong and where they will sound hollow. It is even easier to throw up your arms in defeat. It’s harder to be open. But it’s also better.
Comedy or drama, the strength of a play is in its veracity. You get there by listening hard and letting go.