The Lord is the source of all wisdom, and wants to teach His children to be appreciative for whatever gifts that He has bestowed (Matthew 7:11; James 1:17). Every gift or blessing that we have originates from Him. Thankfulness is good for our souls. It reinforces humility. It reinforces selflessness. It counteracts our tendency to boast. It keeps anger and resentment at bay. It keeps our hearts in a morally sound state. Giving thanks serves as a constant reminder of the blessings we do have. Giving thanks takes our focus off potential things we may desire to have, thus making us happier. It changes our perspective of matters in this life. We must thank Him for everything, even in the midst of sadness, suffering, and persecution (James 1:12; 1 Peter 4:12-19).
We should thank God for keeping us strong during times of evil. He gives to us the strength to endure harm by His all sufficient grace. He is working things out for the good of those who love Him. He is working things out to His eternal glory. If we refuse to give thanks to God, then already existing bitterness will fester in our minds and so rob us of the peace that surpasses all understanding (Philippians 4:4-8). A refusal to show heartfelt gratitude is one of the biggest mistakes that one can make in the Christian walk. The preaching of the gospel is to be done in thanksgiving to God. The gospel itself is a call for all people to give thanks to God.