I ignored my girlfriend for most of valentine's day
Did you have any reason to ignore her?
We were fighting all day and I was pissed off therefore.
It is understandable that when you fight you might not feel like celebrating the next day but ignoring your girlfriend is not the right thing to do. It will not help your relationship and it could cause you more problems.
Yes I know that now but back then I thought my actions were right at the time.
It sounds like you might regret ignoring her a little bit. Which is a good thing, she was probably so hurt that you ignored her on such a special day.