First, evaluate what has been happening in your life and the stress you may be experiencing. You said you "recently started to take the bus" and that leads me to believe that it is a new experience, it was at night and you were feeling unsure and that led to the anxiety.
We see far too many TV stories which center on pretty disturbing things and it's time for a change. Confidence is your best protection against anxiety of this type and, perhaps, you might need to take a self-defense course to help with it. It's not a bad idea and it provides exercise which benefits you in terms of both physical and mental health. Plus, you'll meet people.
Courses specifically meant for women would be the best idea. Consider it.