Haise Sasaki is an amnesiac and remembers nothing of his true identity, but if he accepted his ghoul side, wouldn't he regain his memories, his original identity, and his full power? That would make sense, considering that his Rize was his original personality, which appeared to him during a battle with the S ranked ghoul Orochi, and asking him to accept his true identity as a ghoul. If you know his true identity, good for you don't spoil it for those who don't know. They probably don't want spoilers. If you don't know who he is, read the manga or watch the anime. Tokyo ghoul season 3 just came out. you'll find out in Tokyo ghoul Re:
I waited for someone else to answer this question and no one did. As I said earlier, the answer will be opinion based as there is no evidence we could provide from the anime/manga. However, I will try to answer it best to my knowledge (my opinion of course)
Haise Sasaki, the protagonist of Tokyo Ghoul:re, is a First Class Ghoul Investigator, the mentor of the Quinx Squad and a member of Team Mado. You can predict (from Season 3's first episode or if you've read the manga) that he is self-contained, good-natured individual. As a Ghoul Investigator, he comes off as trustworthy, loyal and devoted. While he portrays a serious demeanour toward his work, Haise is also merciful to some extent, as he believes that an Investigator should not annihilate ghouls unnecessarily.
Haise Sasaki is an amnesiac and remembers nothing of his true identity
Just for your information that if you think Haise doesn't remember that he was a ghoul before, you are wrong! He experiences memory loss yet he is aware of his ghoul side to some extent.
But, unlike Kaneki who accepted his ghoul side, Haise rejects it and seem to be disgusted by his ghoul side as when it tried to convince him to accept it, he ignored it and thought of his mentors (Akira and Arima) to give him courage.
Thus if he accepts his true identity (which seems to be very unexpected for now) and meets up with his former ghoul friends, he might regain his memories and full power.