Telling a story is like synthesizing a gene: you start at the beginning, make your way to the end, and check every letter in between to make sure it makes sense. You do not want anything lost in translation.
Of course, if you want to express yourself properly there are many other things you should consider. You have to be aware of the elements that can promote, enhance, or even repress your story. You need to read it many times for form, content, and flow. It might not be flawless, but you do not want any spots in the sequence that make the reader stop, get confused, or give up. The reader must stay engaged until the end.
Many aspects of the story are purely for the writer to remember when events are supposed to happen. You cannot include every single piece of information in a limited amount of space. Make choices, select, adapt. Remember that it does not need to be perfect, but if you manage to be successful then your product might hang around for a very long time.