I've been there too. It sucks when we can't get a scene just right. Sometimes you just gotta write something that isn't the best and move on. You can always come back later when you've got more of a clear mindset on it. I've found that agonizing over a scene, deleting everything and rewriting a scene/chapter countless times, only makes things worse.
Just because you have a scene that seems shitty to you now doesn't mean your work as a whole is horrible. Who knows? You could even like the idea you've got much later. I remember I once did that, thinking it was so awful but then while editing the second draft, I was like, I actually like this scene a lot. I think moving on will help you a lot or even working on something not related to the main series. Just something fun, maybe even for practice? I know I've had fun writing short stories and one shots with my characters.