It's even better if your main focal point is where the lines cross like my niece's face in the shot below
or the overflowing flowers in this urn in the gardens at Versailles.
Our eyes (for whatever crazy reason) are naturally drawn to that spot in any visual image and it feels good to have the subject there. I might even say it is comforting.
See what I mean? Our daughter's face is where the lines cross. Try putting your subject off center. You may be surprised at how good the pictures turn out. Just make sure you lock your focus on the subject.
Application to writing: There are certain rules in writing that make a story more satisfying. The three act structure is one of those (I picked this one since we're talking about threes). I didn't think it would make my book better if I used it, but, when I applied it to my story, it got much better. It felt right. I might even say that it was comforting. Go figure! What other rules have you found that made your novels better?