Why was Sally unhappy?

M: Well, Sally. Why do you look unhappy?
W: Oh, Hill, I have just had a quarrel with Mr. Smith.
M: What on earth was it about?
W: Well, I have made three bad mistakes so far this week, so he got very angry with me.
M: But I don’t understand. You are usually very careful and never make mistakes.
W: I’m just so tired. I don’t know what I’m doing.
M: Why? Have you been going to bed late these days?
W: No, I’m usually in bed at about eleven. But I’ve been woken up at about half past four every morning. And then I cannot go back to sleep again.
M: Why?
W: It’s my new neighbor, the milkman next door. He gets up at half past four and he always turns the radio on loudly. And it’s difficult to ask him to turn it down. I don’ t know him yet.
M. If you don’t want to see him, write him a letter. I’ll help you write the letter.
W: OK. Let’s try.