Joss Whedon is pretty bummed about how Avengers: Age of Ultron turned out. So bummed, in fact, that it continues to keep him up at night, nearly twelve months after the movie hit theaters.

“I was so beaten down by the process,” Whedon revealed while speaking at the Tribeca Film Festival. “Some of that was conflicting with Marvel, which is inevitable. A lot of it was about my own work, and I was also exhausted.”

Although it wasn’t received as well as the first Avengers, Age of Ultron still did respectably at the box office, grabbing more than $1 billion in lifetime gross. Even still, Whedon, who has directed several successful projects outside of the MCU, feels disappointed by the end product. Here’s what Whedon had to say:

I think that did a disservice to the movie and the studio and to myself. It was not the right way to be because I am very proud of it. The things about it that are wrong frustrate me enormously, and I had probably more of those than I had on the other movies I made. But I also got to make, for the second time, an absurdly personal movie that talked about how I felt about humanity, and what it means, in very esoteric and bizarre ways, for hundreds of billions of dollars. The fact that Marvel gave me that opportunity is so bonkers, and so beautiful, and the fact that I come off of it feeling like a miserable failure is also bonkers, but not in a cute way.

Damn, Whedon. The director became so jaded by the time the movie came out he swore off the Marvel-verse for good, even though friend and actor Mark Ruffalo begged him to come back.

No matter how much you disliked Age of Ultron, know that nobody is harder on a project than the person who created it. In this instance, Whedon agrees that it didn’t live up to the first Avengers, and recognized that it was time for him to step away.