I had a thought while shooting last night. I have an 8.5' in my basement but often play at a friend's shop, where he has a 7' Valley with Penguin rails and I think 4 1/4 pockets, so a tough table. Now when you get shooting good, and only shoot on one size table (say the 8.5' in my case), you start realizing, "hey, this ball is 4" from the rail and 3.5' from the pocket. If I hit/rub the ball like so it goes in." No need to take an aim line or look at a pocket because I know how to move a ball 4" in a given distance. No need for visual focus because you know how to hit it. I'm lazy by nature, figuring out the most efficient way to do stuff, etc. So this laziness is easily fed and leads to not aiming. The dastardly thing is, this is a mistake, but you keep making balls, so there is no negative feedback. The lazy, no aiming rewards you, and quickly leads to a bad habit of not aiming, because you know how far to push a ball over in a given distance. You've got your HAMB certificate so why waste time with all this aiming stuff? Your mind begins to wander and you start getting worse shape. You had no baseline (where you aimed) to start your shape from, so the CB just ends up somewhere close instead of where you wanted it. These small mistakes add up, and 3 or 4 shots later, you're doing trick shots to keep your run going. Kind of like painting yourself in a corner, you're fine at the beginning, but sooner or later, you're stuck.
Another bad part about making balls while getting lazy and not aiming (or not having your intention set): When you play on a different size table, all those shots you were getting away without aiming no longer go in. You'll think your aim is off, but your aim isn't off, you've got into the habit of not aiming. It can be sorted, but you don't want to be in the middle of competition when you realize what's going on because it can be tough to overcome. So a takeaway is, always aim, even if you don't need to. The aiming should be a part of your PSR, even if you don't really have a structured PSR. It's way too easy to get lazy and it can wreck havoc on your ability on different size tables, gives sloppy leave, etc.
To add another layer to the onion, it's not just aiming, it's choosing your intention and deciding what area demands your focus, along with patterns, back up balls, 2 way shots, strategy and the myriad of things this game makes us think about. Focus on too many things and you soon feel like your brain is dripping out of your ears and you'll be praying it works. Focus on too little and you'll fall into bad habits. What a difficult simple game!