Cold shower in the warmer season or cool in colder when you need to refresh and keep energized. You can't keep working or study when you feel too warm. The best performance and you will stay alert it is in cooler temperature. When we perform our mental and physical functions, we use glucose. Excessive heat and unwanted cold are not equally challenged. Cooling down requires more energy than warming up.
Our bodies work to maintain homeostasis therefore we use a large amount of glucose. Glucose is used for mental processes, while exposed to heat our capacity for cognitive functioning is reduced, affecting our decision-making abilities.
In cooler environment your cognitive function performing better.
Therefore, taking a cool shower improves your cognitive thinking and at the same time energizes you and keeps your mind refreshed and focused.