go to details in necessary time

we say, don't go to the details in unnecessary time, try to adhere to the trunk. why?

 

that's because when you are going through the trunk and unexpectedly fall into the branch, this would break the continous understanding and thought of yours towards the trunk, so this doing is not good. try to avoid it. this is also the so-called separate of concerns. we should concentrate on our sole concern once at a time. don't step through the level or modularity.