The sin of acedia, primarily a working of Evagrius of Pontus. Evagrius was an interesting character, who felt himself saved from being vainglorious and other problems by taking the advice of a woman, and becoming a monk. Naturally, that didn’t stop other christians pointing fingers and branding him a heretic later on.
The Demon of Acedia was known prior, and has been defined to mean many a mental condition, but the basic christian definition was “a state of restlessness and inability either to work or to pray”. Evagrius’s particular concern was with monks, and he distilled the major problems down in Eight Logismoi, with this written about the Noonday Demon:
The demon of acedia, which is also called the noonday demon, is the most burdensome of all the demons. It besets the monk at about the fourth hour (10 am) of the morning, encircling his soul until about the eighth hour (2 pm).  First it makes the sun seem to slow down or stop moving , so that the day appears to be fifty hours long.  Then it makes the monk keep looking out of his window and forces him to go bounding out of his cell to examine the sun to see how much longer it is to 3 o’clock, and to look round in all directions in case any of the brethren is there.  Then it makes him hate the place and his way of life and his manual work. It makes him think that there is no charity left among the brethren; no one is going to come and visit him.  If anyone has upset the monk recently, the demon throws this in too to increase his hatred.  It makes him desire other places where he can easily find all that he needs and practice an easier, more convenient craft. After all, pleasing the Lord is not dependent on geography, the demon adds; God is to be worshipped everywhere.  It joins to this the remembrance of the monk’s family and his previous way of life, and suggests to him that he still has a long time to live, raising up before his eyes a vision of how burdensome the ascetic life is. So, it employs, as they say, every [possible] means to move the monk to abandon his cell and give up the race. No other demon follows on immediately after this one but after its struggle the soul is taken over by a peaceful condition and by unspeakable joy.
Going by that description, seems to me that the Noonday Demon is still with us. Perhaps if that was shifted to the Demon of Noonday Naps, everyone would be all kinds of happier, and less restless. I’m a firm believer in naps m’self. They are good for everyone, and since most employers are firmly in the camp of forcing workers to be up and productive at awful hours of the early morn, official Noonday Naps would be extra beneficial, allowing for many to catch up on sleep, and allowing the naturally early risers a nice refresher or rest time.
Cultures which embrace the concept of siesta have done the right thing, cooperating with the Noonday Demon. Why fight, when the reward is a lovely nap? Atlas Obscura has a nice article up about the sin of acedia.