The discussion centers on the common concern among advanced mathematics and physics students about losing fluency in foundational concepts as they progress to higher levels of study. Participants share experiences of forgetting previously learned material, often noting that skills not regularly used tend to fade, a phenomenon likened to the "half-life" of knowledge retention. Many emphasize the importance of revisiting fundamentals through practice problems or teaching others to reinforce their understanding. The conversation highlights that the last concepts learned are often the first to be forgotten, and some participants express surprise at their diminished recall of complex subjects, even those studied years prior. Overall, the thread underscores the necessity of continuous engagement with foundational knowledge to maintain proficiency in advanced topics.