Sgt. Pepper
All you need is love.
I also wanted to mention that based on my experience, spirits who have returned to the physical world from the spirit realm can stay as long as they want and go wherever they want. Of course, they have no physical limitations, nor are they limited to linear time. Based on my understanding, human spirits can generally choose whether to cross over into the spirit realm or remain on Earth, but there are spirits who become stuck in the physical realm and need the assistance of a psychic medium to cross over. The following factors are what I believe contribute to the presence of earthbound spirits: (1) There are some spirits who don't realize that they are dead because they died unexpectedly and so they are in shock and are confused. They initally don't understand what has happened to them and it takes them a while to figure it out; (2) Some spirits are upset and scared of dying unexpectedly and are in denial that they are dead; (3) Some spirits have unfinished business, such as wanting to let their loved ones know that they're okay or feeling obligated to watch over their loved ones; (4) Some spirits are angry and are seeking justice or retribution for their death; and (5) Some spirits prefer to linger around the living because they miss being alive or because they feed on the negative emotions of the living. Finally, the last four factors are why I believe that a spirit's experience is primarily determined by them, and it can be positive or negative depending on how they handle their death and what kind of person they were in life.
