Something's going right...

...when you get one of these coming up off the back deck.
As often happens first thing in the morning, I struggled to operate the camera and lens I'd grabbed - it was a macro lens, which needed a bit of on-the-spot calibration to focus on infinity - and by the time I'd stopped faffing around... 
I suspect you're all too familiar with what's coming: the rainbow had all but disappeared, it failed to put on a reprise performance, and the opportunity was lost. So technically and aesthetically, the photo might not be any great shakes, but the rainbow itself put on quite a spectacular show at the time, and made for a great way to start the day.
Saw a rainbow in the same area some 3 or 4 years ago, and this one was very unusual in that it formed a perfect semi-circle arc of light, with no fading light gaps at all. It was brilliant ROYGBIV light from one end to the other.
I was down at the beach at the time, and although there was nothing impeding my view, the only camera I had was my iPhone, which couldn't fit in the whole arc from end to end. A 28mm lens just doesn't have the spread required.
In general, the best camera may well be the one you have with you at the time - I have no argument with that - but that's a long way from saying you have the best camera (or lens) for the shot.