In my previous job, I was actually put on a performance improvement plan. And, I'll be honest: without going into details, the concerns expressed were completely justified. I wound up straightening up enough to complete the PIP successfully...but it also forced me to take a hard look at the situation, and come to the realization that I'd been in that job too long, and was getting bored with it. So I began casting about for opportunities, and secured a new job in a much better place.