"It helps me to get your input on how I can improve. But, it surprises me that you think I need to work harder. I demand a lot from myself, and I always try to go beyond the call of duty. Can you isolate an area where you feel I'm not working hard enough?"

"It's good that you want more authority and the responsibility that comes with it. But you need to convince me that you can tackle more. To do that, we'll proceed in stages. First, let's try a test run and see how it goes."

You confront a back-stabbing colleague who spread a rumor about you:

"I have evidence that you said something false about me to others. Rather than focus on what has happened, I'd like your word that if you ever have anything negative to say about me or my work, you will level with me first. Do you agree to that?"