But be not thou far from me, O Lord - “O Yahweh.” Others - all others - have forsaken me, and left me to perish. Now, in the day of my desertion and my peril, be thou near to me. See Psalms 22:11. This is the burden of the prayer in the whole psalm, that God would not leave him, but sustain and deliver him. Compare Psalms 22:1.
O my strength - Source of my strength; thou on whom I rely for support and deliverance.
Haste thee to help me - Help me speedily. Come to support me; come to deliver me from these dreadful sorrows. This is not necessarily a prayer to be rescued from death, but it would be applicable to deliverance from those deep mental sorrows that had come upon him - from this abandonment to unutterable woes.