Having achieved a lot, why am I still dissatisfied?

Following is an excerpt from a samvaad (dialogue) session with Acharya Prashant.

Questioner: Sometimes we start off as something, then we set a target. Then we achieve it, and once I’m there, I still look for something else. And once I’ve received that something else, I’m here again looking for second something else. So, what am I actually looking for?