David was in a political crisis when he wrote this psalm. He was under attack from enemies and his reputation in Israel was low. He was being ridiculed from within the nation and endangered by enemies outside the nation (Psalm 69:4). David takes responsibility for his own foolish contributions to his current predicament (Psalm 69:5). He is desparately hoping for God to move to save him. He feels overwhelmed, but still trusts in The Lord (Psalm 69:1-3). He is swimming in the flood, head barely above water. His soul is in turmoil because he realizes that as a leader his choices affect the nation.
Faith is bigger than our impossible circumstances. It trusts that God will deliver. David may be facing ridicule from his enemies, but he is more concerned with knowing God's faithful, steadfast love. That is what is carrying him through this painful crisis. Circumstances may overwhelm us but God can faithfully pour out His abundant care. And in that assurance David trusts.
The psalm begins with overwhelming feelings of dread (Psalm 69:1-3) and it ends with confident praises, trusting God not only to save, but to build up His people and covenantally lead the nation to thrive (Psalm 69:35-36). The journey from fear to faith ends in worship and trust. Nothing can shake the soul that is resting confidently upon God's sovereign shoulder.