For me there is only one true rule of photography that I always try to not to break, read on...
Oh yes, the rule - "Always carry your camera with you". If you are truly passionate about your photography then it is not a just an interest but a way of life and you never know when the next opportunity to make a great photograph will present itself.
Creative Photography is all about spontaneity and if you don't have your camera with you to grab the decisive moment then guess what? Bang goes a chance of making a visually stunning image that will never return again.
Talking of the decisive moment some words from the great Henri Cartier-Bresson himself; "Photography is not like painting," Cartier-Bresson told the Washington Post in 1957. "There is a creative fraction of a second when you are taking a picture. Your eye must see a composition or an expression that life itself offers you, and you must know with intuition when to click the camera. That is the moment the photographer is creative," he said. "Oop! The Moment! Once you miss it, it is gone forever."
These days most people always have a camera with them anyway, in their smart phones. Of these, the very high end devices are getting really good indeed and for the majority of people smart phone cameras are more than good enough for their purposes. However, for those us for whom photography is a way of life, we will continue to use traditional cameras and lenses as they still produce superior quality and provide the versatility we need in order to capture moments effectively and create the level of beautiful imagery we desire. Meantime the gap between smart phone camera capabilities and those of traditional camera systems continues to narrow, so one day who knows?