One of the biggest mistakes that most novice writers make is to create characters that all sound exactly like they do. This makes for flat-footed, uninteresting dialogue. Also, remember that people don't speak in complete sentences. You must learn that broken sentences and sentence fragments are your friends when you're doing dialogue. Another mistake that inexperienced writers tend to make with dialogue is they put emotional keys under the character, e.g., Susan said sympathetically, David said a little angry.
Actors simply hate that.
Unless there is some line that can be mistaken because it can be read two ways, then it just isn't worth putting in the description. If the line is ambiguous, then it might be worth putting a descriptive word in there. But aside from that one exception to the rule, I try to eliminate that kind of direction from scripts because it's considered an insult to the actors if you load your scripts with too many emotional keys. It also slows down the readability of the scripts. You can certainly give the attitudes in the shot descriptions, but don't keep repeating them throughout the dialogue.