Doxylamine
"Diphenhydramine didn't work for me so I tried doxylamine. First night took one 25mg pill and was out within the hour, got a full eight hours but woke up super groggy. The groggiest lasted most of the next day, definitely wasn't worth it. I tried it again two days later with only half a pill. Had the same great sleep with only minimal grogginess. I've continued to take 1/2 a 25mg pill 2-3 times a week when I know sleeping with be a struggle with great results. I'd recommend anyone who experiences the sleep hangover to try a lower dose before writing it off."