How do u leave someone that u love so much but u can see that u no longer have future together?

I think me and my partner has reach the phrase where we no longer care for each other. I won't lie that I still have feelings for him. But i can feel that he’s changing, the way he act, the way he talk, the way he reply. He no longer show interest and as much as I wanna be with him I feel that I no longer wanna talk it out, or asked why he acted the way he did. Feels like im just gonna waste each other time. Should I just let it go? Or wait for him to break up with me?
How do u leave someone that u love so much but u can see that u no longer have future together?
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