You should avoid nicotine and caffeine before bedtime. This means no smoking before bed. The drug nicotine, which is found in cigarettes, is a stimulant and it will keep you awake. You should also avoid caffeine. Caffeine is found in foods such as chocolate , tea, and coffee. There are also some drugs, such as pain killers, that contain caffeine. Some experts think that it is a good idea to avoid caffeine completely because it can stay in your body for up to 12 hours.