It’s a very good idea to ask God for serenity, but it won’t make much practical difference until you get in the habit of opening your hands to receive the serenity you’re asking for.
“God, grant me the serenity to accept the things I cannot change. . . .” Serenity prayer
“I am leaving you with a gift – peace of mind and heart.” John 14:27 (Jesus at the Last Supper)