Answer:
The person who wrote this diary entry clearly suffered a horrible day.
Already at the beginning of the text it says "Today was not a good day", it also uses expressions like "I already dreaded it", "to make it worse", etc. Apparently everything on this person's day is being bad.
He or she has to endure that Pat, who is this person's sister, makes fun of the pain he or she is suffering, and that the dentist uses his tools, which cause a lot of pain, to make a hole in the teeth.
This person couldn't even eat his favorite food.
The only thing that made this person's day happy was that Pat would have to clean the attic.
