Panchan your not alone. You'll find many on this website that have seen these shadows. They seem as if they playing hide and go seek. They also seem to anticipate your movement and you barely get a reall good view. I have seen this all my life, but it took my wife and several other people with me at different times to confirm that it was not in my mind. I spent years afraid to mention these shadows, for fear off sounding crazy. They seem harmless. I wouldn't worry.

I have experienced shadow for the 1st time about 25 years ago. Since then, I have experienced the shadows quickly passing by me while I am watching TV or reading a book. Just last night, I have experienced one of the most frieghtening experiences since 25 years ago. I can feel their presence when they are around me. On one occasion they have spoken to me when asked a question, but falsely.

IT is really very scary and it is hard to talk to people about because first thing they think you have lost your mind when you tell them about such an experience.

I get the same thing out of the corner of my eyes allll the time as well as seeing full figures standing random places. I also get the feeling that I am being watched usually first before I see dark masses or flickering out of my peripheral. If it is happening all the time, and it bothers you, just say out-loud, "I can't deal with you right now, please leave me alone." If more stuff starts happening, and you need help feel free to message me.

You could be seeing a ghost. My friend had a ghost in his apartment. She wore a sun dress and played with the light switches or it could be shadow people.
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There is nothing to be scared of because they are in a different dimension and unless they are poltergists they won't try to harm you. If it was a poltergist you would already know it by now.