You shall not be afraid of the terror by night,
Nor of the arrow that flies by day,
A thousand may fall at your side,
ten thousand at your right hand,
but it will not come near you.
I will be with him in trouble;
I will deliver him and honor him.
With long life I will satisfy him,
And show him My salvation.—Psalms 91:8,16
So much depends on what "it" means.
God has not promised that He will deliver us from trouble. Toil and trouble may be our lot (Romans 8:25). God has promised, however, that He'll be with us "in trouble,” will deliver us from harm, dignify us with His love and satisfy our deepest longings for a "long life"—life that will never end.
The real you—the remembering, feeling, thinking part of you that the Bible calls your soul and you call "myself"—is indestructible! It will be guarded forever. Arrows may fly, you may die, but "it" (death and destruction) will not come near you. No harm will come to your soul (1Peter 3:13).
Jesus expressed the same thought with a wry paradox: "Some of you will be put to death... But not a hair of your head will perish" (Luke 21:16-18).