Phanta Rhei or everything flows
Ancient Greek philosophy suggests that we cannot step in the same river twice, because it flows and it continuously changes and you could never touch the same water. Furthermore, you change yourself and that's a different person who's entering the river every time. This is what I feel every year about the course "Introduction to turbulence" - it's always a different one. Unfortunately, I do not teach "introduction to turbulence" course this year, hopefully next October.