It's What You (What They) See

 

"It's not what you look at that matters, it's what you see."

~Henry David Thoreau

    Not only is this quote great for application in life, but I think it can also be used in writing.
    Even when writing in third person narration, you could improve descriptions by describing the thing/person/place as the main character would see it. For example, maybe when the main character sees one kid in a park tease another, they would be reminded of being bullied themselves long ago and get angry. Or if they saw a tree with thousands of bright green leaves, they might become sad because they're reminded of a long-gone friend who loved to climb such trees. Or if they saw a rabbit, the main character could become happy and laugh at the memory of something funny that happened the month before involving a rabbit.
    Such observations and how they react to it can show readers the character's personality, their past, and what makes them tick.
    What would your main character see in an old, dusty book? Dark rainclouds? A cat? An old record player?