Lyric discussion by ShirleyAwesomeManson 

i think this song is about a mysterious girl who is a bit crazy but in a good way and about a boy who keeps chasing other girls but actually there is only one girl that he really wants. he's afraid of being hurt tho (or afraid of what everyone else might think of their relationship) and therefore won't give them a chance as he prefers to go for easy targets - normal girls, thus:

Keep your head and stop it spinning round Keep your eyes wide open and you'll see her

i think the second/third stanza refers to these two in the future realizing how the opportunity to create a great relationship has disappeared. now that they're adults they regret that they didn't give themselves a chance