For example, you can go out to photograph Barn Owls, sometimes they appear and start hunting early, sometimes they don't. When pursuing an objective I have experienced failure, success and all of the shades between the two.
But sometimes circumstances conspire and nature allows you to get it right.
One such time recently was when I was photographing a pair of nesting Whitethroat, without pressurising the birds I was able to get fairly close. The light was good, the birds were coming and going with frequency, the nest was situated below some teasels that they were using to shimmy up and down to the nest and finally the background allowed me to use a wide open aperture.
All images taken with a remote shutter release on a tripod.
As I have said on many occasions, for me, perfection does not exist, but also for me these shots are close to knocking on the door !.