Is FDR's famous quote actually good advice?

Fear is always necessary because it leads to caution; the enemy is uncontrollable fear. FDR's comment led to America ignoring the "rear" or what was happening in Europe and the isolationist attitude that the US stayed in until the Japanese bombed Pearl Harbor. People who ignore things around them because they don't want to be seen as being fearful are people that like sheep are led to the slaughter. Fear is a good thing and only uncontrolled fear is bad.