I’m convinced that all the gospel-centered grace talk is true. Works (success or failure) don’t forfeit or gain God’s blessing. God gives eternal life to anyone who trusts Jesus for it. Scripture teaches that our best efforts are worthless (Isa. 64:6). Christian obedience results from a thankful heart, but there is a problem if we don't think about thankfulness in the way God intends for us.
There is a wrong way to think of thankfulness. Call it guilt-driven thankfulness. This is what a mother does when she is upset that you don’t call enough. She tells you how thankful you should be for everything she has done. She reminds you that she carried you in her womb, fed you, and clothed you. She is right. You should be thankful, but you probably won’t be. You may call her more often, but only because you want to avoid her guilt trip. Guilt-driven thankfulness commands thankfulness, but it doesn’t change your heart. You won’t always feel thankful. So, how can a thankless person become thankful? There are three ways you can try to deal with your thanklessness, but only one of them will lead you closer to God.
First mistake: When you don’t feel thankful, you can return to rewards and punishment for motivation.
Rewards and punishments can help you to look obedient, but they will never change your heart. God wants obedience that results from the heart. This is the work of the Holy Spirit (Gal. 5:16–25). The New Testament seeks to motivate Christians with the truth of the gospel (for an example, see Col. 3:1–11). I can assure you that returning to rewards and punishment to motivate obedience will never produce love and thankfulness. It will burn you out. It will not be the obedience that results from faith (Rom. 1:5).
Second mistake: When you don’t feel thankful, you can question your salvation.
Questioning your salvation can destroy your hope. At its best, it can lead you to turn to Jesus for salvation. But questioning your salvation, in itself, won’t make you thankful. If you’re not sure you’re a Christian, trust Jesus for salvation. If every time you feel thankless you question your salvation, you need to seek your pastor’s guidance and instruction in better understanding the Christian faith.
The only good option: When you don’t feel thankful, you can pursue thankfulness through love and joy.
There is a lot of Bible, history, and theology here in the background, but what you need to know is this: love, joy, thankfulness, and desire go together. As you come to understand the gospel more, you will realize that you don’t have to be thankful for God to love you. God loves the thankless (Rom. 5:8). When you pursue the joy God gives, you will become thankful. This is what the gospel offers. Salvation is about eternal joy. God offers you a life of love and joy (Psa.16:11). You receive this life when you trust in Jesus Christ for salvation. So when you don’t feel thankful, don’t worry about it. Turn to God in prayer. Read Scripture. Seek to know him. Seek to love him. Seek your joy in him. Trust that God will give you joy, and you will find a thankful heart willing to obey his commands.