I've deployed multiple times into combat and dealt directly with survival and fear. I experienced two types of fears, crippling fear and a guiding fear.
The guiding fear was a helper. It aided decision-making and helped me to stay alive and well in dangerous situations.
The crippling fear was a killer. This is the irrational fear which causes you to believe their is a gun pointed at you from every window and a bomb behind every rock. It's not a useful fear and it overpowers the instincts you trained hard to instill.
Here is how I know I should live fearless - God loves me. God didn't create me so fear would stop me from doing what He has placed me on this earth to do. There isn't any illusion or irrational fear that can stop me from boldly moving forward towards the things God has put in my heart.
God proved His love when he placed his Son Jesus on a cross where he was tortured, died, and rose again from the grave. No one else has done this for me. Not my parents, not my wife - no one has demonstrated that type of love for me except God and Jesus.
If you are struggling with crippling fear - right now pray to God to lift fear out of your life and show you His love. Accept His love through Jesus and move forward. Do this. You will not regret it.