Has anyone else experienced this?

That second when you realise that you really can’t just wing it, and you actually have to calculate something, or take it more seriously.

Buying a few rolls of insulation for the loft, then having the moment of “wait, this isn’t just two rolls worth, I have to actually add this up, and order for delivery”

Loading up the car for a trip to the dump, then noticing that it’s riding a bit low, and finding out that 9 bags of rubble is actually 50% of the total kerbweight.