We are all focused on hormones, but perhaps it's something to do with neurotransmitters?
Dopamine, which controls pleasure, reward and anxiety .
Epinephrine, which is involved in the fight or flight response. Epinephrine is what makes lovers' hands sweat, causes hyperactivity and your hearts racing.
Serotonin, which is associated with mood, sexual desire, appetite, sleep, memory and learning.
Main reason I mention this, if it were all hormonal, I would think we would have discovered the magic combination by now.