I am naturally a "risk analytic". I do not take risk unless I know everything I could possibly know about the event and weigh the benefits to be much greater than the risk. Another reason I prefer CDs to stocks, but that's a different story.
Any situation that takes me out of my comfort zone is always riddled with fear. My comfort zone consists of things I've come to expect everyday, i.e. grad school activities, work, church and home. Anything remotely distance to this becomes a risk, traveling is one. My common sense gets clouded with doubts and in my mind, I quickly think of the zillion things that could go wrong. The what ifs, maybes and the assumptions.
Interestingly, that is also one of the reasons I travel. Not only to learn about places and cultures, but also to understand that different does not mean wrong.
Fear of traveling is like fear of the unknown. We are quick to judge, even hate what we don't know. Traveling has taught me to be patient, less judgmental about peoples way of life and accepting of cultural differences and beliefs.