Well I think the song is a memory and a fantasy. We know the drummer wrote the song in honour of his girlfriend, personally I think he is recalling the first time they had s** because of the laughing and smiling. Its says "as we say all our goodbyes" I think this means he wishes he got to say goodbye to her properly, hez picturing holding her in his arms just like that night, but he knows he has to wake up, he can count the hours on his fingertips till he wakes up and it all becomes just a memory again, the song keeps referring to her as an angel and the line "keep breathing, just keep breathing..." I think to him this dream is real, she is there again and he needs her to keep breathing because he can't loose her all over again, also "like a dream of you i had, could suggest there as been others" catching fireflys together maybe.