Fear drives or influences all of our thoughts and actions.  Fear of death. Fear of man.  Fear of the LORD.  One or a combination of these fears are the roots of everything we do, think or feel.  Fear of death is the God-given instinct to avoid danger in order to survive.  It becomes a problem when it begins to usurp the fear of the LORD when it becomes a weapon in the hand of our Adversary to enslave us—

“…the one who has the power of death, that is, the devil, and deliver all those who through fear of death were subject to lifelong slavery.” Hebrews 2:14 ESV)

As Paul Tripp puts it,  “Fear is a good thing in the face of danger, but it makes a cruel god.”  (Tripp, Paul David. Suffering . Crossway. Kindle Edition.)

Unlike the fear of death, the fear of man cannot coexist in any degree with the fear of God—

“The fear of man lays a snare, but whoever trusts in the LORD is safe.”(Prov. 29:25 ESV)

“Nevertheless, many even of the authorities believed in him, but for fear of the Pharisees they did not confess it so that they would not be put out of the synagogue; for they loved the glory that comes from man more than the glory that comes from God.” (John 12:42-43 ESV)

Fear of man test:  Do you ever do things that you would never think of doing if someone else was around?  Do you ever entertain thoughts you would quickly dismiss from your mind if everyone could read your mind?