This is the first example of how it is better not to be alone. You get into an accident and you are alone. Nobody can help you. This may happen, for example, to an old woman who lives alone and who falls down the stairs and breaks her hip. There is no one who can help or call for the right help immediately.
10 Car, s'ils tombent, l'un relève son compagnon; mais malheur à celui qui est seul et qui tombe, sans avoir un second pour le relever!