The song is purely about the love he had for her and how he pushed her away by smothering her by over analyzing everything she says and believes in using "chemicals" as a metaphor for his in depth analyzing. Questioning if it is really love and making him insecure and killing what they really feel for each other instead of seeing the bigger picture and meaning of their relationship and their love, all because he has been hurt before and did not believe in true love anymore - "love was illusion of a hopeless heart". "She says something that knocks me dead" is her saying that she really loves him and that he has no reason to worry -putting him at ease and making him realize what he's been doing to them and how much he really loves her and she loves him. Really love this song and its meaning. It is like that in the begging- in the getting to know stage if you really love someone- many of us make that mistake over analyzing everything in order to make sure that person really loves you back instead of enjoying every second and falling in love spontaniously. Keep it going guys! Love the band!