Haggai 2:5 (Berean Study Bible)
And My spirit remains among you, do not be afraid.
Fear is the opposite of faith and those two cannot coexist. When the Lord commands us to not be afraid it's not a pious platitude but a command. A field commander may order his troops to have fortitude but not be able to anything else. When God commands us to be be resolute He also empowers us to be brave. To be fearful while walking in the Holy Spirit is a slap in God's face and an insult to His grace.