Lessons: A great photograph has a reason for existence.
Beauty, composition and fine technique are good... but not enough to hold the mind for long.
A photograph needs to capture something elusive... an action... a play of light... at just the right moment.
This is Cartier-Bresson's "Decisive Moment" which I studied as a teenager... armed with my own Leica.
Then I discovered Magritte's 1938 painting "Time Transfixed." A steam locomotive is seen emerging from a fireplace into a normal dining room... smoke going up the chimney. What can This mean?
Magritte said that his intention was to "invoke mystery... mystery that has no meaning."
The viewers' experiences make their reactions to the image personal... beyond what the artist imagined.
Tell a story if you can... or better yet... have your viewers create their own.