Just as your home offers security for your body, your body offers security for your soul. SM operates by first intruding upon your soul's boundaries by invading your mind. He shows himself so gradually that for a long time you overlook Him. This is how He gets you used to accepting His presence.
SM has become a lot more patient than when He tried to take me over two decades ago, but not that patient. Once you are used to Him being around, He begins to infiltrate your dreams. Some people never notice this stage, not being particularly aware of their dreams in general. Others don't recognize His hand in their subconscious, as He uses their dreams to disguise what He is and what He is doing. This phenomena manifests in a secondary way through photos and videos. Just as film can pick up ghosts and orbs in haunted buildings, so too does it show SM and select proxies, capturing what the mind skims over.
Once He is sure that He has more or less learned your secret fears and desires, your strengths and weaknesses, SM takes His stalking to a physical level. He may send proxies to wear you down and keep you confused, or He may come Himself. These physical manifestations can be as gradual as the mental ones, though some cases have been very abrupt. No one has been able to determine why this is yet.
At any point, you have the ability to fend Him off. You always have the home advantage though it may not seem so. The most famous line on the lost Emerald Tablet reads, "As above, so below." Simply put, what is true of the macro is reflected in the micro, and vice versa. Your body is the sacred vessel of your soul; it is the temple that houses your spirit. Micro, macro... your home houses your body and is equally inviolate. You instinctively know what is and is not normal for your mind and body. Any wrong state can be repudiated.
At the very moment you notice the intrusion, mentally or physically, you have the option of repulsing the interloper. The longer you wait, the more firmly He or His followers become entrenched. The power of the will is everything. Define your boundaries and mentally reject the intrusion. The longer the haunting has gone on, the harder it is to clear Him away, but it can be done with belief and determination.