Take the picture below for instance. I was out the other night taking pictures of an abandoned building and I turned around just at the second that this car drove by. Had I not had my camera handy I would have missed the car and the sunset would have been over before another one drove by. Sometimes great pictures can be recreated but many times you only have one chance. Next time you go for a walk, bring your camera along, you just might see something unique.
This is also crucially important when taking pictures of people. Having your camera on ready to go before anyone knows a picture is going to be taken is very important. I wouldn't have caught the picture below if I was waiting around for the bride and groom to pose before I pulled out my camera. Because I had my camera on ready to go I caught the bride and groom just at the moment they kissed. A lot of people also put up lame, fake smiles when they know a picture is going to be taken. If they don't know the picture is going to be taken, and you have your camera ready, you can catch them with a real, genuine smile. The bottom line is: when your around people, don't just have your camera with you, but have it ready go, you never know when you will miss that special moment.