Betrayed by a friend

Psalm 55:1-23
It is not an enemy who taunts  David - then he could bear it. But it is his familiar friend, a man, his equal, his companion.
But I call to God, and the Lord will save me. David put trust in the Lord, and believed God will save him, redeem him.
Put your burden to the Lord, and he will sustain you; he will never permit the righteous to be moved.
But you, O God, will cast them down into the pit of destruction; men of blood and treachery shall not live out half their days. But I will trust in you.
Above and beyond all his other fears and troubles, the treachery of a trusted friend - one who also loves God - has come like a knife to the heart.
The psalmist is torn by conflicting emotions: fear and longing to opt out of the whole situation; and the desire to see his enemies worsted.
But trust eventually wins - for friends may be faithless, but not God.
Why?
Enemy are friends but I call to the Lord.
Even enemy are many but I believed that God will cast them down. I trust in the Lord. Psalmist fully trust in the Lord.
Friend are not trust, but God is worthy to be trusted and praised.
How?
Put my burden to the Lord, for He will sustain me, and I trust in Him.