Just felt compelled to say a few words on paying extra, or giving tips.
I normally pay exactly for the services rendered. However, there are times when I just decided to give 1 or 2 red notes on top of agreed price. There are no hard and fast rules.
As to why I do that, it is usually because I felt like it. As easy as that. Maybe something just clicked and I felt happy. Happy because of the conversation or the service or the positive feelings I get. In short, because I "song"