The bottom line
The main sleep hormone is melatonin, and the main way to stop natural melatonin production is through light exposure at night. Specifically, the blue part of the visible light spectrum.
Give your brain a chance to get into sleep mode! Your brain’s pineal gland can produce melatonin for up to 12 hours if you let it. All you need is darkness. And if darkness isn’t an option (e.g. if your have a light or two on, or watch some TV at night), blue light-blocking glasses are an excellent option. Really — everyone with sleep issues should at least try them for a few days, for 1-3 hours before bed, since they’re cheap and side-effect-free.
(This review will be updated shortly!)