Literature review and originality
It all accounts to got much effort you believe you put in to your work. 

Doing a good review isn't at all easy. It involves a whole lot of work to


collect relevant studies
collate them to groups
assess originality
connect the dots
produce illustration
coherently present the information


If that isn't enough, getting permission from authors and publishers to reuse relevant figures is another hassle. To add on, it would be an ordeal to manage 100+ references without a reference management system like LaTeX/BibTeX. 

The point is that as you go through this process, you'll notice that your skill would gradually improve over time. I'm actually  going through this process at the time of writing this post. I came across a couple of double publication, extensively overlapped concepts, and inconclusive studies. These sort of items are the ones I filter out. 

Hope this helps.