Pick one small action to work on — it could be a fingering pattern, a rhythm, a series of pitches — and focus exclusively on that thing for thirty seconds. Set a timer and stop when it goes off. Reset for another thirty seconds. Spend a couple or three days working on these tiny focus exercises, then bump your time up to forty-five seconds or a minute. This is an extemely efficient manner of practicing: the repetition of tiny focus sessions teaches your brain the steps in the muscle memory sequence that it needs to learn to make whatever you’re focusing on seem natural and easy. There is no “overload” because you’re keeping the sessions very small. If you use a timer (highly recommended!) it gives you an objective stopping point. It’s hard to argue with a timer. And we tend to feel really stupid when someone (spouse, kids or strangers) catches us arguing with an inanimate object.
There is a time when more general practice, or focusing on an area or a broader skill set, is appropriate. But, when you’re just starting out with lessons or learning on your own, or when your training your brain to focus, or when you feel the urge to make a serious dent in a trouble spot, the key is to keep it very small — shorter than you think you are capable of doing — and zero in on one point that you need to learn, and listen actively to what you’re doing.