Psalm 45 is attributed to the sons of Korah. Some theologians such as C.S Lewis relate this psalm to Christmas, such as the birth of the great warrior and the great King: Jesus Christ. The truth is that this psalm is a total exaltation to God, a special song for the only God and King.
The psalmist said:
My heart is inditing a good matter: I speak of the things which I have made touching the king: my tongue is the pen of a ready writer.
The psalmist begins by asking God to overflow His heart with a good word, and this is a good start, since he let himself be inspired by God at the time of giving his song, because we as mortal humans can only give good praise to God only if is He who inspires us to do it.