Read the whole psalm and see its five layers: prayer (vv. 1-7; meditation (vv. 8-10); prayer (v. 11); meditation (vv. 12-15); prayer (vv. 16-22). In our Christian lives there should be a balance between prayer (talking to God in Gods presence) and meditation (thinking about God in Gods presence).
Verse 11 is central to the prayer: “For thy names sake, O Lord, pardon my guilt, for it is great,” the psalmist says. He invokes Gods nature, for that is the reality to which Gods name is pointing, and asks that God will be who he isnamely, a merciful God: one who will forgive his sins.
The prayer is repetitive. I am not always happy when I hear leaders say in prayer meetings, “Keep the prayers short because we want to let everyone have a turn” (or words to that effect). It isnt always or even usually the biblical pattern that prayers are short. Repetition in prayer is not something to be ashamed of or embarrassed by: only if we think there is some magic in repetition does it become “empty” (Matt. 6:7). When were talking to one another, we often repeat ourselves in order to emphasize something; so when were talking to God we can do the same. See how often the psalmist repeats himself. He tells God twice that hes waiting on him (vv. 5, 21); he asks for pardon three times (vv. 7, 11, 18).
The prayer is basically a cry for help, interspersed with praise; praise to God for being the sort of God who helps those in trouble. Breaking it down a little, we could say that first the psalmist waits for guidance (vv. 1-7), then he thinks of Gods goodness (vv. 8-10, 12-15), and then he pleads for grace (vv. 16-22).