The user can exert a force on oneself instead of pushing off another surface, literally "pulling on their bootstraps". By Newton's Third Law, it would be impossible to exert a force on oneself just to move around. To move, one would need to touch another object and push or pull on it in order to cause movement. User does not have to worry about that, they can knock themselves down by slapping their head, lift themselves by pulling their hair, dodge by pushing their hip, move by extending and moving one's arm in a direction, etc. This may extend to other objects the user is holding onto.