Yang, by it's very nature, will eventually expend itself. That goes for people, too. We need to rest. And if we are yang for too long, we eventually become exhausted and collapse (yin).
The best yin is deep and restful sleep. This essential part of life is often ignored as our modern lifestyle encourages us to work and play hard. There's so much to distract us, when everything is available 24-hours a day.
Power napping can really help to top up your batteries. If you do not think you have the discipline, you could try other methods. There is a product I have used for many years to help this - Recharge (I'm not on commission). This teaches you a simple method to quickly recharge your batteries. It is not a substitute for sleep, but can help you if you feel burned out.
Get plenty of rest..... and be happy.