I was taught, when actually shooting the shot, to look at where I am striking the cueball, to see the tip hit the cueball. I mean, if you don't, then how do you know where you struck it? The object ball isn't moving, so once you have aimed why look at it again really? If you are referencing it for your aim, you have to get back up and down again to adjust anyway, so what is really the point? I mean yeah you can see both balls I think fairly easily, but the focus should be where and how were are stiking the cueball I think.
So, the key was focus on making contact exactly where and how I had determined I should when aiming, preparing, and going down on the shot. But, to trust that alignment and don't mess with it after getting down to shoot. And also, be conscious of how I am stroking it, keeping my body in control, head still, follow through, hand hitting the chest at the end of the stoke, etc. I don't know if the person who taught me this ever evolved away from it. But, it sure worked for me at the time to develop a monster stroke and consistent game. He actually played this way and was one hell of a world class player too.
There were no low deflection or carbon fiber shafts back then, in prehistoric pool days, so when you needed a powerful stroke to cover distance, or move the cue ball a lot one way or the other, we were always aiming somewhere crazy to adjust for the deflection. Especially once you developed a powerful stroke. lol