Research shows that exposure to excess light at night ups your cancer risk. One Harvard study found night-shift workers had a 23 percent greater risk of breast cancer.

It may be because your brain releases the hormone melatonin, which inhibits cancer cells, only in darkness.

Get your eight hours nightly, in complete darkness. That means no lights (including a TV or computer) while you’re getting your shut-eye; just seconds of exposure to light can stop melatonin production.