Many theories about feelings exists and it can be a little bit confusing to make sense of all the different opinions (see Wikipedia). I am going to present a view that is informed by NLP and has proven useful in my practice over the years.
Stripped to the bare bones we can say that feelings are just information. They are feedback that informs people about their experiences.
Seeing feelings in this light, it doesn’t make sense to label them good or bad. They just are. Feelings tell you something about what is going on around you and propel you to take action. The following is a schematic view of how feelings come about.