Put your hand, palm down, on a table.
Make a tight fist with that hand. Put out your ring finger from the fist so it is the only finger not a part of the fist, while continuing to keep the fist tight and your hand on the table.
Try to lift that ring finger off the table while leaving the fist on the table.
It is physically impossible unless you are not making a tight fist.
You can look at your finger as long as you want and tell it to move, but it cannot.
This is what it is like for quadriplegics, paraplegics, and others who have lost the use of a limb.
Or watch a video featuring the parent of a child with Tourette Syndrome. See the utter anguish of the parent as she listens to her child lose control in a crowded room, knowing that her child is absolutely helpless to prevent the outburst, and hating it all the same. I’ve ached at the agony in the parent’s face. The agony of embarrassment, and the agony of loss.
Or watch a child defend a disabled parent out in public, not using words, but subtly protecting that parent from stares and unkind looks by the placement of his body, shielding the parent from the looks and giving the offender a wordless, withering reprimand.
Watch the elderly. How do they handle the fast pace of life in a city? Do you ever see an elderly person pause, perhaps before stepping out into a crowd, or before stepping onto or off of an escalator? Do they notice that they are seen as obstacles in other people’s progress? What expressions do you see on their faces as they navigate a mall or a train station or a tourist attraction?
Take the time to sit quietly in a crowd and watch these moments in life. Be aware of what it means to other people to get through one single day. What efforts must they make to survive where you unthinkingly traverse? As you watch, make notes. Don’t try to be clever. Simply record what you see. Interactions. Reactions. Distractions. Emotions. Always look for the emotion attached to any action. Even when there is no emotion, note that. A teen cuts off a mother with a stroller, completely laconic about what he has done. What is the mother’s reaction? A woman on a cellphone drives in fits and spurts in traffic. What havoc is she causing? What are the reactions?
Empathize with others in your life, in your wider circle, and you will be better able to empathize with your characters. You will also be better able to create characters with whom your readers can empathize. Most importantly, there will be truth in your writing, without which your writing is stunted.