It keeps you from peace and faith. Exactly where Satan wants you to be. Peter didn't need to fear when he walked on the water but let his surroundings dictate to him what he should do instead of continuing to look to the Lord. The woman who touched the Lord's garment was afraid because the Lord knew someone had touched Him and wanted that person to confess who they were. She thought she was in trouble, but He just wanted to show others the power of God in how she was healed through faith.
Fear is caused from a lack of faith and trust.
God brings us through things and to places to overcome fear. Sometimes they're all too familiar, so out of habit we sing the same old tune as soon as the music starts playing. Time for a new song. Years of conditioning has made you believe the lie. We must search the scriptures, know the truth and renew our minds with truth for a whole new mind set.