"Eliminate bright overhead light after 11 p.m. Retinal sensitivity increases the longer you've been awake, so even dim screens late at night can activate the brain's clock as strongly as morning sunlight. Huberman cites a Cell paper showing that light hitting the eyes between 11 p.m. and 4 a.m. "suppresses the release of dopamine" and activates the habenula — nicknamed the disappointment nucleus — which "makes us feel less happy and more disappointed, and can lead to certain forms of depression." The practical fix is to place any lights you use in the evening low in the room rather than overhead, switch to dim warm-toned sources, and avoid bright phone or screen use after roughly 10 p.m. Source: Andrew Huberman, Huberman Lab, Master Your Sleep & Be More Alert When Awake"