Moving backwards or sideways can get you hurt. First, backwards means you cannot see what you might trip over, and you cannot see obstacles or people behind you. Moving sideways only means the attacker has only to change direction. He will be moving faster than you can in taking diversionary movement. Better to learns how to parry an attack. See my post above for a link to a thread where I explain how I was trained in the Corps to respond to a knife attack. I know it works.