Enter into his gates with thanksgiving, and into his courts with praise. Give thanks to him, and bless his name.
Worshippers in the temple did not stroll straight into the presence of God. They came to gates, then to courts, moving from the ordinary world into the place where His name was honoured. The psalm borrows that architecture to describe something we do with our attention.
Thanksgiving is the gate. Not the destination, the entrance. Which means gratitude is not mainly a response to a good day. It is a way of arriving. You bring it with you, the way you would bring a key.
That reframes every reluctant morning. The psalmist is not asking whether you happen to feel grateful. He is telling you what happens when you decide, before you feel anything, to begin there anyway.