"To understand painful smile painted on my
Add 'the' between understand and painful. It'll flow better.
"To understand what is so harsh and what
are my fears,"
Change it to: "To understand what's harsh and what my fears are"
But seems you're rhyming 'fears' to the next line, I suggest: "...and to understand my fears"
"And why did I choose to smile through the
Change it to: "And why I chose to smile through the tears."
"You might someday feel the way I feel,
But I fear, old scars are never going to heal."
Love the ending so much. Great write 5/5 Keep writing :)