Mark Hamill gives us a hint as to Luke's frame of mind when we pick things up in Star Wars: The Last Jedi saying that he has not completely turned his back on his old ways and gone to the dark side. He is just very spooked by some bad choices that led to some catastrophic consequences and that ultimately stripped him of his confidence.
After teasing us with just a glimpse of the Jedi Master in Ach-To by the end of Star Wars: The Force Awakens, the last known Jedi is set to be front and center of the upcoming Rian Johnson-written and directed film. But many fans are still puzzled by the significantly changed Luke -- from the optimistic and devoted follower of the ays of the Jedi to a skeptic who boldly declares that the Jedi must end. Now, Hamill provides us a bit of context as to what we can expect from his character once the next episodic film rolls out.
Sitting down with Disney Insider, the veteran actor explains that despite all the ghosts that he is trying to run away from, Luke's fundamental personality has not really changed, it's just that "his life experiences have shaped his outlook the same way they do for all of us." And while he does say that he believes that its time to get rid of the Jedi and their ways established ways, that does not mean that he has abandoned being first and foremost, a good human being:
In hindsight, it would be redundant for Luke to turn to the dark side. The character has been at that crossroads before when Emperor Palpatine baited him in unleashing his anger in Return of the Jedi. But unlike his father Anakin, who fell for Sidious' conniving ways, Luke courageously declared that he'll never turn to the dark side and that he is a Jedi like his father before him. Pushing him down the dark path after that could be seen as undermining everything he fought for in the original trilogy. Additionally, the cast has repeatedly said the events of The Last Jedi will be unexpected, so there might be something in its narrative that we have yet to see happen in the franchise. Be the exploration of more morally gray areas or something else that Johnson came up with.
It won't be long before we get to know the answers to some of these mysteries (granted there is still the JJ Abrams' directed Episode IX), as Star Wars: The Last Jedi is just a month and a half from debuting in cinemas. On top of the specifics of Luke's failed attempt to rebuild the Order, thanks to the betrayal of Ben Solo/Kylo Ren, we can also expect the emotional reveal of Rey's parentage, as well as, the conclusion of Carrie Fisher's involvement in the franchise.
Source: Disney Insider