Have you ever wondered what an Artist had in mind when he / she creates a work of art? The Artist may indeed have strong feelings about what he / she is making to show the rest of the world. Is it important for you to know what he had in mind? Does that make it more enjoyable or less enjoyable?
Before I answer these questions I would like to suggest that Art, (referring now to visual Art) is created for a reaction to / for or against a person, place, thing, event, or even another period of time. Since the beginning of time, in the History of Art, there are many Movements which signify a kind of thought that was prevalent by the artist of that period.
Each period in history, produces art of the culture and focus of that particular period. For instance during the Renaissance, art, literature, philosophy and architecture would focus on secular and humanistic aspects of society. In this European Art World the image was very realistic.
In sharp contrast, during our recent history, there was a school of painting known as Abstract Expressionism developed in the United States, specifically New York. These artists, broke away with a tradition, where a painting always had to have a recognizable image. They favored no recognizable image but rather made "the gesture" and the energy in the work of art the most important value. They were free to express their spontaneity and individual psyches.
So what does all this have to do with viewing a work of art. First of all we each come to view a work of art, no matter what the "history" of the work, with our own experiences and psyches. When we react it may bring up something pleasurable or not. If for instance we view an abstract work and it brings up a reaction, that may be enough in and of itself. However if we also know the History of the time it was made, that may also add to our enjoyment of the work.
So back to the original questions. One can seek enjoyment of viewing "art" on many levels. The more you know about the period and intention of the Artist, the more you may bring to the enjoyment of the art. However, more importantly, if the painting evokes a feeling, pleasant or not, or it speaks to a place inside you, that is enough. The Art indeed has done its job; that of allowing you to react!