I only missed a flight once and i felt pretty stupid at the time as well. I took the metro to the airport and then I realized that I forgot some medicine.

I barely had time so I headed back but I messed up pretty badly because my medicine was the whole time in my backpack I just didn't find it or was so sure that I forgot it.

Then I obviously missed my plane since I didnt get there 3 hours earlier. I missed one day in the beautiful city of Rome, but it wasn't that bad. I think I was high at that time