The work that marine biologist and deep-sea diver Rhian Waller does illustrates this well.She studies life in some of the deepest and coldest waters on Earth.How does Waller control her fear and stay safe in these high-risk situations?"It comes with practice," she says."It's knowing exactly what to do when something goes wrong. We prepare well for each of our expeditions, and we try to minimize the number of risks we take."