The experts say it can be from physical or emotional problems or just lack of sleep. Some people say a cup of coffee helps. To some, it can be more serious, such as poor circulation to the brain. The topic is interesting.
Yes, especially if I have to get up really early. I just wait for time to pass to allow my brain to wake up. I did a hub on brain fog. I think it's either sleep deprivation, anxiety, or overload. But for me, I'm not a morning person so the brain is just not ready to function before sunrise. :-)
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