I was having a hard time getting cross eyed stereograms to work, and stubbornly kept trying until after 2 or 3 months I finally succeeded. It was so neat I looked at thousands of images right away. That, however, has ruined my ability to learn how to see parallelview images, singe my eyes just default to crossed when I try to align the elements. I’ve not been quite as stubborn about it, but trying has also been a lot more frustrating.