The natural internal clock that controls our 24-hour cycle of sleep and waking, circadian rhythms are easily upset by changes in schedule, and they're greatly affected by light and darkness.

Alcohol on the other hand, tends to disturb your sleep cycle, leading to frequent waking, and a poor night's sleep overall.

Coffee later in the day also disrupts our sleep cycles, which continues the vicious cycle of waking up feeling unrested and needing that cup of joe to wake yourself up.