How precise should a drawing be?

When The Mountains meet the Sea, (pastel on paper 65 x 45cm), 2016

I'm persevering with my determination to make work in varying sizes and because I find it difficult to understand how to scale up my marks, I am using small drawings and working from them as a way to overcome this barrier. Because the goal is to keep things loose I am mostly using the colour in the original and just focusing on making lively, bigger work.

As a recall, when I was making the original, I wasn't true to the scene before my eyes as I worked.  I moved things around and eliminated things from the view when it felt right.  So, when I go back to work from the drawing, I find things that I believe in the original don't make as much sense when larger.  A small stroke estimates something in a general way when working small, but feels as if it needs to be defined more when bigger.  BUT LOTS OF PAINTERS ABSTRACT, so why do I find this so difficult?