Hey guys,
you may call me an idiot, but since a while I´m catching myself focusing alternately - or jumping if you will - between the target and the reticle when aiming.
Now I´m a bit confused and thought you might help me out.
I think you mean focusing your attention, which should be on the reticle. Kind of like they teach "front sight focus" on pistols and rifles with iron sights. It's easy to wander between the reticle aiming point (crosshair or dot) and the target. If you are looking at the target instead, the aiming point can float around a slight amount without notice. The floating is less noticeable with high magnification but still applies.
The reticle. Just like irons, your focal point should be on the front sight post tip. The same applies to an optic; focus on the reticle once you have checked your npa and parallax.