A Sin to Be Late?

Today one of my classmates expressed wonderment that I could be "so disciplined in so many areas..." and yet be [chronically] late. "Is it because you don't view lateness as a mortal sin or something?" said she. "You were even late to the first class meeting" -- I don't think it was my fault, or maybe even a fault, that time, but I certainly didn't make a good first impression. She did not understand how I could be such a way. (I will add that she was kind and respectful in her comments.)

Well, I must not have a strong conviction against being late... and I should probably develop one. Here's a few reasons.
Being late is:
1. Not being faithful in the least of things.
2. Rudeness to professors.
3. Disruption to a class.
3. A bad witness.
4. A result of laziness (potentially).

Hmmm... I think I've backed myself into a corner.