Doing it in the morning gets you ready for the day, but showering at night ensures you go to bed so fresh and so clean. If you don’t run warm while you sleep, there’s no reason to think you won’t still feel refreshed the next morning after brushing your teeth and completing the rest of your routine. For some people, though, showering as soon as they wake up is as much about actually waking up as it is about getting clean. If all you need to feel alert in the AM is a cup of coffee, that might not matter.