When I was training for my initial rating, my IFR instructor had to take over manually in cloud when the autopilot gave up on us and wasn't holding course. It was just white outside and I thought it was routine just to fly on instruments. Suddenly all the dials on the panel seemed to jump out and start rotating in front of me in mid-air. I fought the illusion and managed to regain focus after about 10 seconds.
After the flight, I thanked my instructor for doing all the hard work for me when I should really be the one flying the aeroplane. I then told him about the illusion I experienced and asked him how he got used to flying in cloud. To my surprise he told me after he obtained his initial IFR, it took him three years of frequent practice to get comfortable to flying in IMC - and he is a leading (if not the leading) IFR instructor in the country.