when you are in a relationship and you have someone on the side you could potentialy go for incase the relationship fails or so you dont " get hurt." Your girl/boyfriend is your A+ but the sandbag is a B+ but you will take it anyways. A sanbag has everything you are looking for its just you dont want to be in a relationship with them quiet yet...or you need them just for botty calls.
Its okay I dont want you back.. I got my sanbag doing what you should have done.