Good composition in art tends to be a mystery to many beginning artists. Unfortunately, many new artists approach composition as guesswork. Your artwork should never be the product of guesswork.
Composition can actually be a bit structured. It can be studied and practiced and improved. Learning the basics of artistic composition coupled with practice, will lead to you to make well thought out decisions about your own compositions.
When we think of visual art, we seldom think of Plato. Plato, however did present some philosophy on visual art...
One day one of Plato's students asked him about composition in art. Plato's response was, "Find and represent the variety within the unity". We know that variety and unity are both principles of art. Most of the principles of art deal with composition.
But, variety and unity are almost opposites. We know that we need variety and unity in our artworks, but how do we combine together to create good composition? The answer is we must push our work to create variety but keep the variety confined to being unified.