Focus, yes but only when necessary!
I read many times that Focus is the Key to Success. It might be probably true but, in my opinion, only under very specific conditions:
1. You know exactly where you are going
2. You are going in the right direction
3. The path is clear and there are no crossroads or obstacles.
In other words, focus is useful when you have already explored and evaluated alternatives and you can exclude all but one of them, which is the most probable that will lead you to the achievement of your goal.
I believe that focus is required in the execution of a plan, but not when you need to create the plan. In those condition where planning is not an option because of high uncertainty, focus becomes less relevant and practical.
There is a nice book on “Plans and Situated Action” by Lucy Suchman (here is a short summary) that explains what are the circumstances where planning is not adequate. This is the definition of Situated Action:
”Situated actions”: every course of action depends in essential way upon its material and social circumstances. Rather then abstracting action away from its circumstances and represent it as a rational plan, the approach is to study how people use their circumstances to achieve intelligent action. How do people produce and find evidence for plans in the course of situated action”
The methaphor used to illustrate the concept of situated action is that of “sight navigation”. Typically, sailors cannot rely on a strict plan as weather and sea condition can vary unpredictably. Therefore they only have a high-level plan (i.e. going from point A to point B) and they sail in a “reactive” way, adapting to the current situation. In this type of activity, the sailor needs to perform so called “continuous planning”, namely continuosly adapt the planned action to the current situation.
My point is that unconditioned focus is useless in situations of uncertainty. Even if you wanted to stick to a plan, there is in fact no plan!
One picture that exemplifies this situation comes from IDEO:

Basically, you need first search for opportunities, evaluate them and then choose the most promising one and focus on it until new opportunities shows up. In evaluating opportunities, one has to figure out if they are deemed to failure and this must be done very fast.
In other words, you need ways to deal with uncertainty and this can be done only by getting more data about the situation. This can only be done through experiments whose goal is learning more about the environment and the situation itself.

