It is a bit sad that many times people have difficulty being in the moment and appreciating every acheivement. You may want to research topics like “finding happiness in everyday life” and adding a bit of mindfulness practice at the end of your sessions. Who knows? It might even help you in dealing with this type of client and this type of reaction.
From the little bit you provided us, I would tell you to be positive. You are doing a great job. I make an effort to end ever session with a positive thought and express my sincere appreciation for the time the client and I have shared.