We've all been there--the final bell just rang, and now the hallways are alive with a sea of students, each struggling to reach their locker, the buses, their rides, their cars, even just the door. If you aren't careful, you can be swept up in this.
A useful visualization for this is what I call the "Rock of Gibraltar" spell. As you walk down the crowded hallways, see yourself as much bigger and tougher than you are. See yourself as a "rock", impervious to pain and attack. Project linebacker energy. Make sure you walk with your eyes on something other than the floor and your back straight--good posture adds to the impression of strength.