1 Thessalonians 5:18
…in everything give thanks; for this is God's will for you in Christ Jesus.
God's desire for us is to see His will manifested. A key to seeing God's will manifested is in thanking Him for what He has done for us through Christ Jesus. Thanksgiving is a key to faith. To walk in God's promises you must see what He has promised in His Word as already done for in the eyes of God everything you have in Christ is already an established fact. For example you are redeemed, you are not going to be. What God promised us in Christ was established 2000 years ago through His death, burial, resurrection and ascension. So to live a life of thanksgiving don't focus on what you see in the natural, focus on what God's Word has said, and start thanking Him for what He has already done for you through Christ Jesus. Those who are grateful (full of gratitude), will be faithful (full of faith).