You have to coordinate your two eyes and many parts of your brain in order to see 3D pictures. 3D viewing stimulates many areas of the brain, so most people find it very pleasurable. The stimulation makes them feel alert, yet relaxed. Well, people don't feel good when they can't get it.
Many people give up too quickly.
You need to give your brain time to process and recognize the image. Can you remember a situation when you were looking at a confusing visual scene and it took you a while to figure out what you were seeing. Your mind had to grope around for a while. Hmmm, I can remember experiences like that. It was confusing, but, also, exciting . . .