YOUR BIG ERROR MIGHT ONLY SEEM LIKE A MISTAKE.
I can’t tell you how many times I’ve written a scene, thought “oh my gosh, that is awful and I can do nothing with it,” and then been moved to more deeply contemplate my characters and their choices. That contemplation sometimes helps me realize I had things right all along (for reasons I never realized), and if I didn’t…. well, I’d rewrite.
You can only achieve success by writing, and getting feedback. (From yourself, and others.)
Writing junk is the only way to create quality... consider the alternative. You can always stop writing forever, if you hate making "mistakes".