I went through this cycle last night where my allergies were bad so I wanted a Benadryl but I knew it would make me sleep and I had homework to do so I was trying to finish it before I took Benadryl, and then it got to be 2 AM before it kicked in so I couldn't sleep and than I couldn't get up this morning AND the class I had was cancelled so I totally could have taken my Benadryl and quit working earlier.