"Don't worry," Tyler tells her. "It'll all be okay."
Tyler's a dreamer; he sees the future in terms of laters and tomorrows and never-gonna-happens. Caroline's a realist; she sees the future in terms of next weeks and too soons and she fully grasps concept of eternity.
She's afraid to let him in, afraid to love him knowing they can never last.
Tyler tells her it doesn't matter, tells her he loves her now and they should live in the moment. "You've only really got today, Care," he whispers one night when they're outside. "Be with me here, right now; don't think about what might happen down the road, take this adventure with me."
Tyler's kisses are intoxicating, and Caroline allows herself to get caught up in all of his idealistic philosophies.
Tyler's a dreamer and Caroline's a realist, and deep down they know they're doomed no matter what.
In the meantime, they have an infinite number of moments until doom catches up to them, and sometimes Caroline lets Tyler convince her to put on her best running shoes and run as fast and as far as she can.