I often read books and check emails in the morning.
However, I heard we should avoid such things.
Almost all tasks are divided into two types; brainworks and simple works.
In the morning, sympathetic becomes dominant, that is, our brains are active.
Therefore, we should do brainworks during the morning instead of simple works such as reading books or checking emails.
It is said that these simple works should be done during the evening or night, because parasympathetic becomes dominant in the night.
