Mercy is the act of showing compassion, clemency and kindness towards another person. When God shows us mercy, He demonstrates that He does not treat us as we deserve. He will have mercy on whom He will have mercy.
The bible says in
Lamentations 3:22-23 
, "Because of the Lord's great love, we are not consumed, for His compassions never fail. They are new every morning; great is your faithfulness". God's mercy is great and He will not let you fall into the hands of your enemies. His great mercy and love are from old and He will always remember you. He is a good God and He loves you with an everlasting love. Let your soul take refuge in Him and He will have mercy on you.