out of sight out of mind, that is the main problem with us because we can not imagine what we have never seen.
so, if you want to try imagining a 4d shape. cut off your eyes, through them away, replace 4d eyes and connect them to your brain after that you will see something you can not translate in your mind for a long time, like a small baby who still see a colored picture in front of him without recognazing the distances, spaces and shapes
after a long time of headache your brain will start translating the 3d perspective picture as a projection of 4d objects.