Some 25 years ago, I started practicing and learning my count, reading, etc. I never walked into an actual casino until I felt I was ready to rock'n'roll. I had it down to a science by the time I played my first hand in the casino, complete with charts, statistical data, notes, you name it and I prepared for it! My count was dead accurate, dead on... never off by even one card.
All except for one thing that I HADN'T prepared for! The noises, distractions, etc. I found that the clanging and bells of the slot machines in the background had a definitve disorienting effect on me, the lights were a distraction, along the people and scrutiny. I found that where I had been able to keep an exact count and never go off by even one card, suddenly I was losing the exact count in the actual casino conditions! This was alarming to me and I then started to create diversions and noise while practicing flipping cards at home, take phone calls, whatever... it still took a long time to be able to block out things to focus on what I was doing, maybe about a year or so of infrequent trips.
After a time the lights, the background noise, the distractions are all easily blocked out and you acclimate to be functional in this environment. Anymore nothing has any effect on me and the waitress could whip out her breasts and start singing "The Star Spangled Banner" at the top of her lungs and I won't lose focus or lose the count. The Pit Boss could do cartwheels across the pit while John Phillip Sousa style marching band tunes blast in the background and I will not lose focus or lose the count. Purple flying monkeys could come flying out from the ceiling and...okay... you get the idea.