May those who hope in you not be disgraced because of me, O Lord, the Lord Almighty; may those who seek you not be put to shame because of me, O God of Israel (Psalm 69:6 NIV).
There are two possibilities for a prayer like this. The first one can be sin. In the previous verse David talks about his folly and his guilt which is not hidden from God. When you commit folly or sin, it can ruin those who have looked up to you. Their young faith can easily be shaken up. It can discourage someone to such an extent that he gives up fighting sin, simply because he was discouraged by your failure. Jesus also referred to this possibility when He said: “But if anyone causes one of these little ones who believe in me to sin, it would be better for him to have a large millstone hung around his neck and to be drowned in the depths of the sea” (Matthew 18:6 NIV). Since such a serious possibility exists, you should pray an earnest prayer like David.
Secondly, in the context of the entire 69th Psalm, you have to consider another possibilty for such a prayer. David talks about the troubles of his life. He talks about his enemies who were hurting him without cause. Now when some believer sees a man like David in trouble like that, he would be discouraged to have a walk of trust and faith in the Lord. He might think that the life of faith is full of difficulties with thorns all along the path and might be tempted to live a life of ease away from God. Now David is more concerned about this problem in this Psalm. He prays that the troubles surrounding his life should not discourage someone else who has put his hope in God. Paul, on the other hand, had a chance to explain to his friends that what has happened to him has really served to advance the gospel (Philippians 1:12). But all may not get a chance to do so. Therefore there is great wisdom in praying like David prayed: Let no one who hopes in God be disgraced because of me.
Finally, beyond the scope of the two reasons mentioned above, there is a third possibility. David was finding life difficult because of his zeal for God and His house (v. 9). When you show zeal (i.e. great enthusiasm) for the Lord, it is most likely that people close to you insult you. When that happens, pray that others who hope in God, may not be discouraged by the criticism you face.