Oscar Issac briefly discussed how the characters will struggle in TLJ:
“The characters that you know already: their specific character flaws or their weaknesses get tested. And out of that, I think, you get to see a bit more of who they are. The best way to learn about somebody is to see them in a crisis.”
EDIT:
http://comicbook.com/starwars/2017/04/21/star-wars-the-last-jedi-oscar-isaac-poe-dameron/