Whenever students approach their dissertation professor or guide for help they are usually given feedback on the project that they have worked on. They are taught ways in which they can improve and they are helped to make sure that they do not repeat their mistakes the next time they are working on a project. After all, working on projects is an essential part of academic life and students have to work on projects and reports all the time. If they were to continue repeating their mistakes then all their future projects would be disasters.
Some of these suggestions might need to be implemented immediately, while the usefulness of other suggestions might not be obvious at that moment. It is essential that the student keep a notebook and write all the suggestions down. They can be used in future projects.
Feedback often makes the student change the belief system about a particular topic. He might have trained himself to think about the project in a particular manner and he might have approached his research from that angle. Then the professor discusses a new point of view with the student and the student starts looking at the project from a fresh perspective. That is why students should be talking to their professors, peers and guides at regular intervals during the course of the research so that they can always approach their project from a fresh perspective.
There are times when the students will not agree with their professors regarding the feedback, and in such cases they should write the points down that they disagree with, go back to their labs, do more research on the points and come back with their own views to counter the thoughts put forward by the professors.