Christian apologists like to argue that the gospel writers are telling the truth because no early Christian would have invented embarrassing stories that made early Christian leaders look bad, such as Peter denying Jesus three times. On the other hand, they also like to argue that changed lives of the disciples are proof of the resurrection because only a real encounter with the risen Christ would be sufficient to explain the transformation of cowardly weasels into champions of the faith.
Sadly, they never seem to notice the inconsistency in their arguments. If the transformation of the disciples is proof of the resurrection, then their earlier cowardice isn't embarrassing at all. It is an absolutely essential element in the story. In fact, the gospel writers would have every reason to make the disciples look as bad as possible prior to the crucifixion in order to highlight the transformative power of the resurrection.