How can you tell when it's truly over or when you've finished? [24F] and [29M]

I'm a 29-year-old male in a relationship with a 24-year-old female, and we've been together for four years. During this time, we've experienced quite a lot. For the first couple of years, I found my partner incredible, regardless of his actions—whether it was lashing out at me, shutting me out during his insecurities instead of communicating, or telling small lies because he struggled with trust and often saw himself as a victim. He did try therapy eventually, but it didn't last long. Over the past year and a half, he has made significant changes, and many of those earlier issues have been addressed. However, I find that my admiration for him has waned, and the vision of a future together—marriage and forever—doesn't feel as strong anymore. I feel like I support him in many ways, including financially, emotionally, and mentally. Although he has started to be more emotionally supportive, it took a considerable amount of time and the loss of someone close to him for him to understand my feelings, especially during tough times like birthdays or anniversaries when I just needed some quiet. I'm not really sure what I'm trying to convey with this post. I guess I want to hear from others who might have gone through something similar. How did you realize it was time to move on or that you weren't truly in love anymore? I care about him deeply, and the thought of leaving makes me feel guilty because I'm not sure how he would cope. I just felt the need to share my thoughts.