I saw what I have always thought of as my guardian angel when I had pneumonia at the age of about 8, and she appeared to me as an old woman, sitting on the chair beside my bed, smiling benignly at me as if to reassure me that I was on the road to recovery - and I was from that night on.
Because it was pitch-dark when I saw her, I recall her as glowing with light. This is the way the brain copes with such anomalies - how could I see her if it was dark? She must have been giving off her own light source. Not necessarily so.
After my father died (he peeping out from behind the 'P', who died about a year after my mother), I was working in my studio, kicking up a lot of dust and noise with an air-hammer against stone, when I became aware of some people standing on the threshold of the entrance. I looked up to see both of my elderly parents standing there, also smiling benignly. I removed my ear-defenders and dust-mask, having turned off the noisy air-hammer, then stood watching them in silence as they, in turn, watched me from about 10 feet away. Not a word was spoken, and they turned away and walked out of sight.
I knew it was pointless to chase after them, they would have evaporated. By evaporated, I mean turn into an ordinary, living, elderly couple who I had never met, and would never meet again. The more I had chased and questioned them, the more real and mundane they would have become, until I would have brought them into a mundane reality, including a verifiable history stretching back to the beginning of the 20th century, from which they could only escape by escaping me. The longer I had chased them, the longer their family tree would have extended back through time. I would have woven networks of friends for them - relations and acquaintances, all of whom would have been dragged into the vortex, never to escape unless all links with me had been severed, from generation to generation into the future.
In truth, they would have begged me to leave them alone, and probably eventually had me sectioned under the insanity laws. Or maybe their children would have done this on their behalf, and these children would have never existed unless I had brought them into reality by having the bad manners to create their parents out of thin air, simply by lacking the grace to accept a little gift - no matter how small - from what 'mediums' call the other side.
This is how the brain copes - or more accurately, does not cope - with the paradoxes associated with living and dying on Earth.
All things are possible, but don't bite off more than you can chew. Also, don't be scared of it - it doesn't bite unless you get too close for your own personal comfort.