This Psalm is a cry to God for mercy. If grace is receiving something we do not deserve. Mercy is not receiving what we do deserve. And we deserve condemnation, judgment, and every evil consequence for our sin. But God in his mercy withholds more than we know from us in those areas. He does not treat us as we deserve. He relents, and does not willingly bring suffering or grief to anyone (cf. Lamentations 3:33).
Rather than giving us what we deserved (judgment, condemnation, and hell), God in his mercy gave us Jesus, his gift of grace, forgiveness, and life. God not only withholds his wrath from us, he forgives. He saves. He gives life. This psalm has been answered, is being answered, and will be answered whenever we pray it. Thanks be to God for his mercy!