One rude comment can’t undo a year of work. Don’t let someone else’s sentence rewrite your progress.

Twelve months of work has weight and a passing remark does not, but the remark is recent and vivid, which is enough for it to temporarily outrank everything else. Your judgement about your own progress is unusually easy to overwrite in the hour after somebody is careless with you.

Wait a day before you let any single comment change what you think. Then compare it against the actual record of what you have done. If it contains a useful correction, take that part. The rest can be somebody’s bad afternoon.