Whatever you do it's always connected to something else. You can't do anything in a vacuum.
Every system is made out of small pieces. And it's hard to focus on all those other pieces and dive deep into the one at the same time.
When getting your hands dirty it's best to focus on only that. Forget everything else around and just do whatever is at hand.
But on larger scale it's better to account all that is connected. To reflect how it affects everything around whatever you are doing.
So, to be able to focus on that one thing at the time taking care of the bigger picture beforehand is paramount. You can't just do something and see how it fits in the bigger picture afterwards. It needs to be the other way around.
When you have everything planned in advance gives you the peace of mind working on your thing. You have your constraints set. Then, you don't have to do compromises. It should fit naturally to it's surroundings and compliment the system instead of sticking out of it.
Even though it might take a bit more planning in the beginning it will save a lot of work afterwards. And the end result will also be more uniform system.