One night I brushed my teeth before going to bed.
What was the reason for you brushing your teeth before bed?
My teeth were so yellow and they looked disgusting.
You shouldn't be doing this only every once in a while.  It's important that you brush your teeth before bed every night, otherwise they're going to start falling out!  I'm sure your dentist would agree!
Yeah, I'm feeling the difference. My dentist says my teeth are getting better and I'm making progress.
Brushing your teeth before sleep is a great habit to get into. You do not want all that food sitting on and between your teeth rotting them away as you sleep.