Not many people would hold their ground, let alone look dashing, in such a situation. Neither Tolkien or I would fault you for weak knees. It's the moments of desperation that produce heroism, at least according to Tolkien's beloved Anglo-Saxon model. One does not know how they will endure it, until that moment occurs. Pippin actually explains it later, in saying that Boromir had come to their aid, and it would just have been wrong to scamper off and leave him alone against many foes.