It helps to know why you are creating something. Simple as that sounds I believe that being an artist is not just about mastering technique. You become an artist when you understand why you are creating something. Why the subject speaks to you. Then you can go ahead and develop that story.
It is OK not to know these answers when you are learning your trade. Ask the question nevertheless and let you unconscious mind chew on the answer. In fact this applies at all stages. Keep asking why.
The little study above is an example. There is a surfer at our local beach who arrives each day (it seems) with several Border Collies. While the old surfer goes out to do his thing the dogs roam free to explore the beach. It is a good life I reckon. I started this painting intending to paint the surfer and one of his dogs. Then I realised that I found the dogs to be the reason I was interested in the painting. The dogs were the story. So out went the surfer and the dog remained. Simple.