There's a saying I heard somewhere that you should never let your mother brush your hair when she's mad at your brother. Very true.
I'd like to add that you should never let someone cut your hair when they are upset about their daughter's Year 11 subject choices. Made the mistake of mentioning I was a Year 11 teacher. Obviously, she had been bottling this issue up a bit. And so she started vigorously cutting away and telling me all about the lack of support and cooperation from the school (not mine - another local establishment). I was making sympathetic noises while watching in a slight panic, desperately wondering if there was anything I could do to slow her down, as my locks disappeared in all directions.
Worst haircut ever.