Simon, Simon, Satan has asked to sift all of you as wheat. But I have prayed for you, Simon, that your faith may not fail. And when you have turned back, strengthen your brothers. (Luke 22:31,32 TNIV)
Satan wants to sift the disciples like wheat - he wants to put them to the test, chew them up and spit them out. Jesus tells Simon about this. They are all in Satan's sights. But Jesus has prayed for...Peter, that his faith would not fail him. And those prayers are answered: in the event of Peter's testing, his faith doesn't fail him; in faith, he repents of his sin when Jesus looks at him.
But what about the others? Did they not need Jesus' prayers too? Why tell Simon that they were all vulnerable but that he had prayed only for Simon? The pronouns are deliberate and deliberately disclose that distinction.
The answer is in the commission Jesus gives the soon-to-fall and soon-to-be-restored Peter: when he has turned, he is to strengthen his brothers. Jesus will help them in their vulnerability through Peter, their fallen and restored brother.
We need the community of such brothers and sisters. They are part of the Lord's means of strengthening us in the face of our vulnerability.