I like to see it as love, which might sound simplistic, I think it's the idea that even if he runs, he can't escape love, which may actually be his fear. At least, not without showing (the fear) love, first, the way he is seeing it given to him now. And because she's inspiring those feelings inside him, he runs. It makes me feel like the last two lines are saying that it's going to impact her the same way-- because he ran, she'll always be running too, because love is scarier when you've been hurt before. Maybe that's the reason he runs in the first place.
I like to see it as love, which might sound simplistic, I think it's the idea that even if he runs, he can't escape love, which may actually be his fear. At least, not without showing (the fear) love, first, the way he is seeing it given to him now. And because she's inspiring those feelings inside him, he runs. It makes me feel like the last two lines are saying that it's going to impact her the same way-- because he ran, she'll always be running too, because love is scarier when you've been hurt before. Maybe that's the reason he runs in the first place.