O Jehovah! God of my salvation! Let me call upon you particularly to notice what I have just now stated, That although the prophet simply, and without hyperbole, recites the agony which he suffered from the greatness of his sorrows, yet his purpose was at the same time to supply the afflicted with a form of prayer that they might not faint under any adversities, however severe, which might befall them. We will hear him by and by bursting out into vehement complaints on account of the grievousness of his calamities; but he seasonably fortifies himself by this brief exordium, lest, carried away with the heat of his feelings, he might become chargeable with complaining and murmuring against God, instead of humbly supplicating Him for pardon. By applying to Him the appellation of the God of his salvation, casting, as it were, a bridle upon himself, he restrains the excess of his sorrow, shuts the door against despair, and strengthens and prepares himself for the endurance of the cross.
John Calvin, Commentary on Psalm 88, trans. James Anderson.