I once asked an engineer friend why he's such a worrier and he responded that it's his job to worry. He said " I literally travel down every branch of my design looking for what could go wrong. I have to know when I launch this machine worth millions into the ocean, to be sunk to the depth of the cold sea, that it is going to work and collect data. All of the worry is in the planning prior to the launch." This helped me understand worry a bit better because I seldom worry and I come from a family who worry themselves sick.