The only potential mirror in my garden is the pool of water in the inherited birdbath. Iced-over recently and scummy mostly, it's hardly a looking-glass. As the birdbath is broken, I'm able to lift off the basin and occasionally swill the contents into the nearest flower-bed, hoping that some fresh rain-water will soon replenish my tiny oasis-cum-oracle. Sediment starts to build up again a few days later, with an identical composition seemingly as before, the remains of avian ablutions (a.k.a. pigeon poo), I presume.
“Reflection is the business of man; a sense of his state is his first duty: but who remembereth himself in joy? Is it not in mercy then that sorrow is allotted unto us?”
A number of web-sites give credit to Shakespeare for these words though they don't reference a source play or sonnet. I spent a while searching unsuccessfully for literature study aids to help me translate, convinced that my first impression couldn't possibly be correct : man doesn't remember himself in joy?
Reflection in the human psyche is not as questioning and soul-searching as introspection. It's simply when something that's happened before returns to one's mind. Scientists have proven that man is not alone in learning from the past, as some animals demonstrate cognitive behaviour too. (Who knows if they go as far as asking introspective "why?"s and "why me?"s.)
In short, I don't agree with the quotation. I do believe that the way we perceive what happens in our lives bounces off and creates an image of who we are. In general, the reflection is diffuse and just helps others form an opinion of us; in special cases it's focussed, motivating others to learn from our mistakes or successes. The key word is perceive.
Some may see a dirty, old birdbath ...