Varieties of problems and solving them might be a challenging task. More you flood yourself with problems, requirement of swapping area and capacity to hold all of that increases. At first, solving a hard problem itself is a challenge, then solving two tough problems one advocating left brain and one advocating right brain even might be a more difficult task.

Changing the focus is pain. But changing focus again and again can give you the power of critical analysis for your own work. You work at one corner, solution seems useful then you have to travel far to land on the other corner then you see your solution from different prospectus, this can give a more better way to think about your own approach.

Studying things and getting things done are entirely two different approaches :
When we study we make models of thinking, a hypothetical garden of fruits in our mind which keeps changing again and again until we find such which satisfies our all equations. In this situation when we have formed an opinion or a stable model, it is useful to test against real world problems. But before that its good to solve questions and studying the same thing from different approach or from different focus.
ignoring out that stable model which I am talking about, is easy and more near to natural strategies to solve real world problems when we keep one, while reading concepts or studying basic things. So when we are studying the same thing from different approach we can also choose to keep a different agenda in our mind.
Getting things done is a different approach. We want to solve a thing which is of our interest, though all those models we have developed were developed because we also wanted to solve a problem of our own interest, but just for that we read and observed lots of things which might not fall in our interest. Getting things done is a mapping from real problems of our interest to possible ways of solving problem lying in our mental models.