When I was working in an office in Japan, I worked in a little cubicle alone much of the time. When my boss came into the room and spoke to me from behind my back, I nearly jumped out of my skin. This didn't happen a few times. It happened nearly every time. To his credit, he did what he could to try and warn me that he was coming and even resorted to knocking lightly on the cubicle frame as a last resort to stop from startling me (this worked but he couldn't always remember to do it).
All of my life, I have been hyper-sensitive to changes in my environment. If it is a strong change, like headlights in a dark night, it is often physically painful for me. If it's a mild change, like my boss walking into the room unexpectedly, I get startled. I've also always been very aware of very subtle things which others do not experience. I smell scents others cannot detect until the threshold increases. I can also tell mood changes with extremely subtle cues and the moods of others have a profound effect on me.
In the case of my husband, I can even predict what he is thinking by looking at his face. I'm not talking about generalized thoughts but specific ones. One evening as he prepared to hop into the shower, I knew by his movements and face that he was going to think about a story he was writing while he showered. When he came out, I said, "you were thinking about your story, weren't you?" He said that he was and wondered how I knew since we hadn't said anything about it in the recent past. I could just tell by his state of mind as reflected in his body language.
This state of hyper-awareness can be both a blessing and curse. While I can read people easily, the messages I detect can easily send my mood veering off into a negative direction. I also find that being in a noisy, bright, or visually "busy" place to be overstimulating. The commute to and from my office, which used to be about 12 minutes when I worked in Nishi-Shinjuku, became almost unbearable when it was extended to 45 minutes when my office moved to Kudanshita.
Quite some time ago, I came across a book by Elaine Aron called "The Highly Sensitive Person" (or, HSP). The theory and content of this book was a revelation for me because it explained so much about why I was different from most other people in terms of my propensity to be exhausted, depressed, or overwhelmed when others in my situation were apparently unfazed. Prior to reading this book, I didn't know that others weren't having the difficulties I had because their nervous system didn't process stimuli in the same manner as mine did. I just believed there was something wrong with me psychologically and that I was inferior in my inability to handle daily life.
For me, life is like living in a noisy room with overly-bright lights and a wall paper pattern which is so ugly and fussy that it gives me a headache to look at it all the time. This isn't an emotional short-coming on my part (though people around you like to view it that way), but just a difference in my biological wiring. People who called me oversensitive or thought I was a big baby for getting stressed out under conditions which annoyed them but didn't push them over the edge aren't living in my skin and have no idea what I go through because they are comfortable in their certainty that everyone experiences the world exactly as they do.
The best thing about knowing you're an HSP isn't that it gives you an excuse to withdraw or react badly. The best thing is that knowing it puts you in a position to monitor your responses to stimuli and to see an overload coming. You can derail an emotional short circuit before it happens and stop yourself from lashing out at others when the pain overwhelms you. If the people you live with understand what life is like for you, they can know that withdrawing to some place dark and quiet isn't a form of punishment or a means of expressing anger in some sort of passive-aggressive way, but a method of coping with how overwhelmed you feel. It also allows you to know your limits and plan your activities around what you know you can handle. Best of all though, you can stop beating yourself up for feeling somehow less adequate than people who were born with the sense-equivalent of a suit of armor. You know that you were born with the sense-equivalent of a paper dressing gown and you had no damn choice about it.