We were created to walk in fellowship with God, trusting Him for everything in our lives. We were not created with the capability of carrying the heavy load of worry. Many people think of worry as just an innocuous way to spend time but it is actually destructive. When we take the wrong route to handling life with worry, our body reacts with ulcers, tension, disease, and worry can cause us to respond to the people around us with inappropriate reactions. 
Yes, we do need to think, ponder, wonder, and consider…even think with care. But that is different than worry. Psalm 94:19 tells us, “When my anxious thoughts multiply within me, Thy consolations delight my soul.” (NASB) Worry expands within the mind to crowd out trust in God. We begin to think we need to control, manipulate and guarantee that nothing bad will happen and that only the positive will occur. We feel tense wondering if God can handle our situation and even if He can handle it, we wonder whether He really cares and will respond to our need. When fear and distrust of His will for us crowds out trust, worry multiplies and creates destructive forces within us.
That’s why God doesn’t want us to worry. We were created for trust and rest and peace in Him. It’s because God loves us and wants the best for us that He doesn’t want us to worry. That’s why worry is sin. Scripture commands that we don’t do it! If we do, we are being disobedient. Yet, just like many other sins, we’ll never overcome worry completely. But God does want us to learn to diminish it more and more because it is a distraction to trusting Him. In the Bible, that word “distraction” most often defines the word “anxious” (NASB & NIV) and “careful” (KJV) (as in Philippians 4:6: “Be anxious for nothing). 
Commentator Matthew Henry identifies that for us when he says about Philippians 4:6: “Here is a caution against disquieting perplexing care (v. 6): Be careful for nothing…avoid anxious care and distracting thought in the wants and difficulties of life.”
Then he goes on to clarify, “It is the duty and interest of Christians to live without care. There is a care of diligence which is our duty, and consists in a wise forecast and due concern; but there is a care of diffidence and distrust which is our sin and folly, and which only perplexes and distracts the mind.”
Is it a perplexing thought to you to think of worry as sin? Maybe you haven’t considered it that serious before. If so, think about the destructive impact it has in your life.