Dora Bas Rivka Silver O'H
"Well, That's A Load Off My Mind!"
This Psalm is introduced as a "maskil." The Talmud in Pesachim (117a) says that it refers to a form of praise that David would communicate through a spokesperson or an interpreter. In this Psalm, David says that the fortunate and deserving person is the one whose sins have been forgiven and "buried" by his merits. If he repents well enough, G-d will expunge sin from this person's record altogether.
David laments the time he spent procrastinating, rather than confessing his sin (as he ultimately did). His worry and guilt caused him to waste away. He was afflicted both day and night, causing him to wither and wilt. Now David confesses his sin, no longer trying to conceal his errors. (The Radak points out that, of course G-d already knows about our sins. We must confess for our own sakes.) As soon as David started to confess, G-d forgave him! Every person who strives to be close to G-d should make note of this and endeavor to emulate it, lest they be swept away.
David says that G-d is his shelter; He rescued David from his enemies and protects him from all manners of trouble. David advises others to follow in his footsteps; he will share the benefits of his experience. Don't be like a horse or other animal that needs to be muzzled while it's being groomed; the animal doesn't understand that the groomer is doing it a favor! Instead, take David's advice in the spirit in which it is intended. The evil people, who place their hope in their money and in their own power, will pay dearly for that. Those who place their trust in G-d will enjoy His kindnesses and rejoice because of it.