This and the previous psalm  are both usually called "royal psalms."

These psalms are linked by the Hebrew word for "salvation" in 20:5, 6, 6, 9; 21:1, 5.
The word "king" is used in 20:9; 21:1, 7. 
The "right hand" appears in 20:6; 21:8.
Psalm 21 begins and ends with a mention of the LORD and His strength

21:1-7 The LORD is source of all the king's blessings and strength

21:8-12 The enemies are conquered
Are the "you" and "your" words a reference to God or to the king? Whichever view we take may not be that important if we understand that God was the source of all the king's strength and HIs victories are only through Him.

21:13 The LORD is exalted and praised