All photographs are there to remind us of what we forget. In this - as in other ways - they are the opposite of paintings. Paintings record what the painter remembers. Because each one of us forgets different things, a photo more than a painting may change its meaning according to who is looking at it.
A great photograph is a full expression of what one feels about what is being photographed in the deepest sense, and is, thereby, a true expression of what one feels about life in its entirety.