Proverbs 4:23 says,
“Keep/Guard your heart with all diligence; for out of it are the issues of life.”
Your heart is your life! It is what you put in your heart that will determine the outcome of your life.
The reason why it is best to let God be the ruler of your heart. Because when He is, He would give you the grace to only let good into your heart.
Forgive easily, let go by all means. You are giving yourself peace when you choose to keep your heart clean, and when your heart is clean, you are poised for greatness. So do forgive, smile, don’t bare grudges and surely your heart will be good to go.