Having an excitable brain doesn't just mean being excitable as a person. We all have excitable brains to a degree, but some people are more likely to be affected by, for example migraine (1 in 7) and anxiety (1 in 20) and there are many other common conditions where overload is involved. Such as challenges from sensory overstimulation and processing of emotions and information for people with ADHD, autism spectrum disorder, post traumatic stress disorder, sleep and mood disruptions.
When we were babies, most of us will have been told at times that we were 'overtired', but what does that mean? When we're tired, we sleep to reset and calm our brains, so being overtired must be more than just being very tired. Young and developing brains are easily overstimulated and quickly filled with experiences, so there seems to be a point where we can no longer normally process information or experiences, and our behaviour changes. These behaviour changes in an overtired child are often negative, from detached and grumpy to raging and irrational, but last only until sleep resets and restores. However. being overtired doesn't make going to sleep easy and there can be knock-on effects into the next day.
In the overtired and overstimulated state, the brain can't relax and process so it takes a while to allow the backlog of events, emotions and information to process. We often call this an inability to 'switch off', so we understand our brains are running at a high speed, but find it harder to 'switch off' and often can't stop at the point before we overload or get overtired.
Many people pump themselves up on caffeine or other stimulants in the day, but then need relaxants like alcohol to calm down and sleep, so ups and downs are common and although can work in the short term, are not a long-term solution and often don't work at all.
If we're overloaded and overtired, then we're not at our best so maybe we should remember we're not that different to toddlers, filled with stimuli and experiences, and when our excitable brains overload we can have tantrums too, or migraine, anxiety or other problems.