Of the 11 times the phrase 'Be Strong and Courageous' appear in the Bible, 5 appear in the book of Joshua and 3 others refer to Joshua himself. So needless to say, these words must be associated with this courageous man of God.
"Have I not commanded you? Be strong and courageous. Do not be afraid; do not be discouraged, for the Lord your God will be with you wherever you go.” - Joshua 1:9
Fear can easily lead to discouragement.
Discouragement then leads to anxiety,
which in turn can lead to spiritual paralysis.
Once this paralysis has set in, it is very hard to move anywhere with much focus.