John Gill Commentary Psalms 38:21

"Forsake me not, O Jehovah: O my God, be not far from me." — Psalms 38:21 (ASV)

Forsake me not, O Lord
Or continue not to forsake; for he seems to have been under divine desertion, and might be under apprehensions that God had utterly forsaken him; which he entreats he would not, though his friends had forsook him, and his own strength had failed and left him, (Psalms 38:10Psalms 38:11) ;

O my God, be not far from me ;
as to his gracious presence, and with respect to help and deliverance, otherwise God is not far from any of his creatures, being omnipresent.