I Will Fear No Evil

The reason David could say "I will fear no evil" is because "Thou art with me". The reality is that there are things that bring fear to our humanity. In times of fear our blessed Shepherd's presence changes our countenance from one of fear to one of restfulness.
Our confidence needs to be in who He is and not in who we are.. He wants us to not only focus on Him but to yield to Him. The things that happen in our lives are always to bring us into a deeper dependence on our Shepherd. David writes "Thou art with me", the Christian can say "Thou art in me". We are not strengthened from the outside in but, rather, from the inside out.