X-Men: Days of Future Past2014

Kitty Pryde:
Basically, your body will go to sleep while your mind travels back in time. As long as you're back there, past and present will continue to coexist. But once you wake up, whatever you've done will take hold and become history. And for the rest of us it'll be the only history that we know. It'll be like the last fifty years never happened, in this world, in this war. The only person who will remember it is you. Alright, Logan, I need to you clear head and to stay as calm as possible.

Wolverine:
What? What do you mean?

Kitty Pryde:
If your mind gets rocky it'll be harder for me to hold you. You could start to slip between past and future.

Wolverine:
What if I need to get a little rocky?

Kitty Pryde:
Think peaceful thoughts.

Wolverine:
Peaceful thoughts. You have any good news?

Kitty Pryde:
Well, you don't really age so you'll pretty much look the same.

Iceman:
You won't have much time in the past, the Sentinels will find us. They always do.

Kitty Pryde:
And this time we won't be able to run, we'll have no escape. This is our last chance.