Based on my own test experiences and those of my testers, I've noticed the following.
At the start of a test cycle, if your test fails, your likely reaction is:
“Yeah, baby, it failed! Yesssss! I rock!”
At the end of a test cycle, if your test fails, your likely reaction approaches:
“Damn! I can’t believe it failed. We’re never going to get this done in time. ...On second thought, maybe it didn’t actually fail. Maybe I did something wrong, I heard the DBA was doing some kind of maintenance, maybe that was the problem. Besides, the production servers are much faster, I’m sure they would work better. Perhaps if I reboot and try again, it will work. Then I won't have to tell anybody.”
Can you relate on some level? Finding bugs in fresh software gives us a rush. We joke about it; “Let me sink my teeth into your code!”. But after a while, we get tired of finding bugs. We just want stuff to work so we can move on. As we approach the ship date, we start to feel frustrated when stuff crashes. We’re actually…wait for it…disappointed to find another bug. We wish the test had passed.
Testers, be careful. Don’t ever let yourself grow tired of finding problems. When that happens, your ability to investigate diminishes and your team value drops. I call this “Tester Fatigue”. Being aware of tester fatigue is probably all you need to know to avoid it and stay frosty.