In the spirit of "SEEING IS BELIEVING", this video is a stark example of what happens when you do not download and study the manuals and other available information before taking that first flight. The pilot here did not go to a wide open area for the first flight, and did not visually keep eyes on the craft. Watching the controller screen or using goggles does not give the depth perception of your eyes.
Another main reason for crashes is being distracted. It is vitally important to pay continual close attention to your flight. Modern UAVs appear deceptively simple to fly, but they are complicated craft requiring study and training followed by practice.