Firstly, poor sleep is scientifically proven to diminish critical thinking. Secondly, it also impacts on your judgment, and problem-solving skills. And has been proven scientifically to contribute to a weaker immune function. It is known to contribute to weight gain too. But that is not all. Best you beware of high blood pressure and accelerated aging too. The importance of high-quality sleep to your mental and physical well-being cannot be overstated.
If you are waking up in the morning more irritable then that is a result of a lack of sleep. And if you are feeling that you cannot manage your ability to handle conflicts? You can guess what the cause is. Less empathetic? Well add that to the list.