I love writing things on public bathroom walls with a sharpie or paint marker.
Why do you think that it is okay to vandalize the bathroom?
Why am I doing this? I don't know, I just feel like writing. In any case, I have a strong urge to do it.
It is bad to vandalize other's property.  You are an adult.  Just because you want to do something, doesn't mean you should.
I'm obsessed with art. I like start of new paintings and seeing my favorite mural paintings.
I think that you should stop writing on the bathroom walls because it is not okay to deface other's property. You should get some canvas or something instead.