Colossians 3 is jammed full of thoughts about thankfulness.

We ought to be thankful that we have been called to be part of Christ's body - the church (v.15). We are to sing together in corporate worship "with thankfulness in [our] hearts to God (v.16). Whatever it is that God has ordained for us to do in our respective callings in life, we are to do it "giving thanks to God the Father through Him [our Lord Jesus Christ] (v.17).

Thankfulness is a soil in which the poisonous weed of pride does not easily grow. - John Stott

Thankfulness follows contentment. A discontented man is not thankful for anything; but a contented man is thankful for everything.  - John Gill, A Body of Practical Divinity

God’s goodness without His greatness might fail us; His greatness without His goodness would terrify us. - Thomas Adam, The Sacrifice of Thanksgiving

If we could only see our souls as the ten afflicted lepers saw their bodies, we would pray far better than we do…Let us mark what a rare thing is thankfulness. Only one of the ten lepers turned back and gave Him thanks. The best of us are far too like the nine lepers. We are more ready to pray than to praise, and more disposed to ask God for what we have not, than to thank Him for what we have. Murmurings, complainings, and discontent abound on every side of us…The widespread thanklessness of Christians is the disgrace of our day. It is a plain proof of our little humility… Thankfulness is the very atmosphere of heaven. It is also the spirit that is the source of happiness on earth. - J.C. Ryle, Expository Thoughts