You will be able to see ghosts when you become one. It will happen some day. No one gets out of here alive.
A lot of people see shadow people, which are movements that you see out of the corner of your eye in the peripheral vision area, but cannot see when you look at them directly. Have you ever been working and think someone entered the room, but when you look, no one is there? Or see someone walk past you from your side vision, but no one is there?
Shadow people are very dark and hazy, much like a shadow. The American Indians believed they were spirits of their ancestors. Children and animals can see them, but adult humans lose the ability to see them directly.
If you want to see shadow people, just dim the lights in the room and stare at an object on the wall. Do not look to the side, but be aware of what is going on in your peripheral vision area. You may be able to see shadow people when they move past you. American Indians used to smoke peyote to help them to see and communicate with spirits. You could try that, but it is probably illegal.
"Democracy is two wolves and a lamb voting on what to have for lunch. Liberty is a well-armed lamb contesting the vote." -- Benjamin Franklin