While I was snorkeling during spring break one year, a large barracuda suddenly flashed in front of my mask. My heart skipped a few beats and I spun around quickly but it had disappeared. After swimming about 30 meters, my heart again skipped as I saw the stainless steel blade brightly reflect the sunlight. I had remembered that big barracudas rely mainly on instinct when attacking small shiny fish, and a flashy knife in murky water was a perfect imitation of a small fish.
Fear can trigger poor and even dangerous decisions.
Likewise, fear can help us to make good decisions. The key is to be able to tell what we really should fear and then to respond wisely. Decisions based on understanding are usually wise. The struggle is to discover wisdom and knowledge before making a decision we'll regret. Jesus Christ gave a good insight about fear to His disciples as He prepared them to go out into unknown territories and tell others about Him.