Levelling level design

Once upon a time a team of students at the University of Amsterdam were very confident about their game concept, and about developing their game. It was a matter of putting the elements and assets together. Then I told him to think about their level design… and again they answered to me: “the levels… we just need to adjust these and balance, once we got everything on the stage together”.
Again I tried to tell them to start in time, because the levelling and balancing is easily overlooked and  underestimated (while it is actually one of the most fun and gratifying things to do in game design)… but overly confident they left my coach session, then next coach session, they were not present to my surprise. Then two weeks later they came, with dark shades around the eyes.
When I asked them where they were previous week, they almost aggressively defended that they needed every minute they had….. “Level design is very hard to do!” – Then I told them that I told them exactly that, and only then, they admitted and realised that I did indeed. So they learned their lesson, and I learned mine too. I can say or teach whatever I want, they might not hear me at all, if they did not experience exactly that themselves first, one is just not able to hear it.
A great example for thinking this thoroughly through is  Calvin tic-tac-toe flowchart.