I used to always feel ashamed that I'd missed something when the testers came back with issues. I have now changed my mind.
Testers are experts in their area and I'm an expert in mine (I hope!). It's their role to check everything to ensure quality. Besides I should spent less (yes, less*) time testing and more time coding. I should not try to write code that will pass all possible tests (functionality, uat, random, etc) in the first instance. Almost all apps will fail testing to some degree in the first run. Why not accept this and move onto a smaller and more frequent develop/test cycle?
So now, I'm happy that the testers find things. It means that they're doing their job and I'm doing mine.
* Less time, but more effectively.