Here he is talking about meeting a girl and deeply falling in love with her in  a way he does not control, but the video and the lyrics were set in a figurative sense. The video shows him in a hospital setting as a crazy guy. The girl playing a nurse holding a huge syringe as to really "mess him up." Towards the end of the video and at some brief moments inside the video it was clear what the lyrics meant. Even though this is one traditional way of speaking of love, the video clip here tried to show that figurative way of talking about love in image and video.