Essentially, David is calling on God (v12) to stop punishing him (v13) and save him from the consequences of his sins (v8-v11):

Save me from all my transgressions;

do not make me the scorn of fools.

I was silent; I would not open my mouth,

for you are the one who has done this.

Remove your scourge from me;

I am overcome by the blow of your hand.

When you rebuke and discipline anyone for their sin,

you consume their wealth like a moth –

surely everyone is but a breath.

So he is saying: "Please listen to me and stop punishing me for my sins."

There's a lot more to say (like we could talk about David's humility or what he did wrong) but that appears to be out of the scope of your question.

Essentially, David is calling on God (v12) to stop punishing him (v13) and save him from the consequences of his sins (v8-v11):

Save me from all my transgressions;
    do not make me the scorn of fools.
I was silent; I would not open my mouth,
    for you are the one who has done this.
Remove your scourge from me;
    I am overcome by the blow of your hand.
When you rebuke and discipline anyone for their sin,
    you consume their wealth like a moth –
    surely everyone is but a breath.

So he is saying: "Please listen to me and stop punishing me for my sins."

There's a lot more to say (like we could talk about David's humility or what he did wrong) but that appears to be out of the scope of your question.