Which is the most difficult part in writing a research and judging your research success?

In my opinion, the real judge in your research success is how to explain the results obtained during study period.
Despite the brilliant Literature review which you already prepared, and well-organized methodology where used in the study design, as well as the proper listed results, the research still need a real, obvious and convincing ideas and opinions to support the actual purpose behind creating the research idea.
Whatever the resources used in the research body design from literature review till results will not be enough to come your research out into the light.
The role of your creative and distinctive thinking in how to connect those data together and exclude the causes and reasons of resultant data in scientific and logical manner will make the difference.
The research should step forward from being understood by its editor or author to public readers or the concerned group with this type of such research subject.

i think get new Idea, inspiring, Motivation and focus it's first.
to Collecting reference and avoiding duplicate

Abstract

Difficult part of research isDiscussionand Results you justify you results with discussion with the help of previous literature.Youjustify yourresults on the base of the Researcher of any research concluded these results and my results are match or not.justify your results are difficult.

The most difficult part of research is reviewing the literature. It is the corner of any good research. It is the first step to determine the gap in knowledge, practices ...etc. I do not see any impact of a research if it does not build on the preview body of knowledge. We cannot talk about successful research story and impactful recommendations without understanding where we contribute and add. 

Self developed research tool. Validity and reliability of that tool. Criteria to follow items formulation of tools and Data collection.

Constraint resources especially financial is very difficult part of research

Burhanuddin

i think a research work is judged not by its outstanding results. but by the way it is done, by using correct methodology and sampling technique. and i would say it is the difficult part in writing a thesis. if methodology is not correct, then result will be absurd.

your success is determined by how many people read it. how many people cite it. how many people use it in their work. it is judged by the others who access it. hence no specific part of the paper can tell your research success. some body can say that it is a quality article , some body can say that it will have impact but no body can tell about the success. by the way what is success, how do you define it.