And we will beat you!
I took my son to see Speed Racer on opening weekend and since then have had the new version of the soundtrack rattling around my head (which isn’t necessarily a bad thing). One line that keeps coming to the fore is a clip where a bad guy says “You have beaten us Speed Racer, but I solemnly swear that you will pay for our defeat. We will race you again. Soon. And we will beat you!”.
This is analogous to a tester’s battle with bugs in their product. We can spend hours/days/weeks/months/years searching for bugs in the code we are responsible for, but when the next release rolls around there will be a fresh batch of bugs that try to trip you up. They just do not give up.
There is also a line from Speed in the song where he laments “Why do you try to win this race fair and square?” which is appropriate. They don’t because they that is not what they do. Same with bugs. They are there because they always have, and always will be. And the sooner you accept this, you won’t beat yourself up (too badly) when something slips your net and makes it into the wild.