Let the peace of Christ rule in your hearts, since as members of one body you were called to peace. And be thankful. - Colossians 3:15
Dear Jesus, I love how the words, "be thankful" just creep into grand passages about peace from our relationship with you. I try to imagine descriptors of you when you walked the earth and I think one would be that you were always thankful. I cannot see you complaining about a messy house or a messy roommate. I cannot see you stressing everyone out by what you cannot get accomplished. I don't think you ever complained when you were small because your mom cut the sandwich into triangles instead of squares. You never complained and always thanked your Father and people genuinely. I on the other hand am a "chronic complainer." I know it even when no one else notices because I complain in my heart. In fact, I complain so much that I get bored by my own complaining. Jesus, make me a thankful person like you. More importantly, thank you for forgiving my ungrateful heart. I want to live a thankful life because you accept me with a gracious heart. When I do live a thankful life, I feel the peace you talk about too. AMEN
Complaint is really an identity issue. If you see yourself as blessed without merit you will not complain about much. Until God changes how you look at yourself, you won't stop being unhappy with everyone and everything.
Additional Reading: John 14:27, Romans 1:21, Philippians 2:14-18