Personally.. I could tell you about EVERY off stitch I've ever accidentally made in just about every quilt I've ever made, but realize... you are looking at your quilts from the creators artistic eyes. The recipient of such a lovely quilt is just THRILLED that you thought enough of them to make them a quilt at all. They NEVER EVER see the mistakes.
I think no matter HOW LONG a person quilts they strive for "100% perfection"...which is just a non-reality. Each quilt is a learning experience and your skills keep getting better with each quilt.
I think it's beautiful, and you picked great fabrics for the Disappearing Nine Patch. I actually have that EXACT same cat fabric I bought to surprise a feline lover friend of mine.
Take a big deeeeeeeeeeeeep breath. You did a great job, and it looks SUPER NICE!
Fons and Porter have this super funny rule. They call it the "40 MPH Rule). If you have made an error in your quilt go out and hang it on your front fence. Drive by at 40 mph. If you can't spot the quilt flaw when you drive by... then you DON'T need to fix it...LOLOL