"But the one who endures to the end, will be saved"
Notice that the verse immediately preceding this one says that because lawlessness is increased, most people's love will grow cold. So it makes it reasonable that the thing that will endure in the faithful is the continued love towards everyone, while the rest of the world will not be loving. There will be a general sense that you cannot trust other people and only believers will still be loving in that environment. It is that form of endurance that will show that you are saved.
Until tomorrow,
Gil Stieglitz