Life is kind of intertwined with the afterlife. There's usually a ghost in the room with you. Someone you know, laughing at your jokes and listening to music with you. You can't see them though. They can only see you. They are always there. Don't worry, they tend not to hang around if you're doing anything private or intimate or whatever. Ghosts largely respect privacy.
It's sad being a ghost in the afterlife. They are always alone. The world is full of ghosts but they can't see each other. It's like they are on different frequencies, like radio stations that can never listen to each other. So, you're all they have for company. They are there at family gatherings and so on, unnoticed and unnoticeable in the corner. Enjoying the craic but sad really. Did you ever see some old friends from a bus window and wave but they didn't see you as they walked on, enjoying each other's company? Being a ghost is a bit like that.
A ghost will hang around watching loved ones live their lives and then those loved ones die and the ghost is left even more alone. New people move into the building and the ghost is left watching them, like it might a new TV show that has replaced its favourite. This is when ghosts start getting bored and feeling really lonely. This is when they might knock down a picture or slam a door shut. It requires a lot of effort for a ghost to slam a door shut. They have to build up to it for weeks. It's a real event for them. They slam the door and then they observe the reaction of the living. The living usually note the oddness of the occurrence and might remark on it a few times before eventually dismissing it and forgetting all about it. The exhausted ghost's little thrill at the slight acknowledgment will pass and the ghost will sit and pant and recall how easy it once was to slam doors shut and to open them. The ghost will probably wonder which it did more of while alive: slamming doors shut or opening them. The ghost will probably regret all the doors it slammed shut during its often lovely and sometimes unlovely existence; slamming doors shut on other people, slamming doors shut on itself, and eventually having the door of life slammed shut in its face. 'Ooh, I really wasted my life', say the ghosts to themselves. This is usually when ghosts start moaning and rattling their chains and that's when the living call the exorcist and that's when another door opens for the ghost and the ghost goes through it. On the other side of this door, the ghost discovers the after-afterlife. The after-afterlife is just a load of former-ghosts (ghosts of ghosts, if you will) that no longer worry about what they did when they were alive and instead spend all their time worrying about what they did when they were ghosts. 'Ooh, I really wasted my death', say the former-ghosts to themselves. The moaning and the chain rattling starts up again at this point but there is no one to call an exorcist and, even if there was, there is nowhere to move on to. It's a noisy place the after-afterlife and it's getting more and more full.