Shi..s happens.
I was on a 40km trip with a bunch of friends, wind was blowing hard, was really cold and raining a lot so we decided to take a rest at a gas station. Getting there I realized my front tire was just flat. No problem, I had 2 replacements. Disassembled the tire, took the tube out and when I tried to put in the new tube I realized the rim had a hole to fit only presta valves and the replacement tube had a schraeder. My cousin had a repair kit, problem solved... NOT. Looked for the hole on the flat tube, reached for the repair kit, repaired the tube, put air on it, the air is gone. WTF happened??? Me and my friend where chatting during the repair process and did the repair somewhere else, not on the hole... Did it all again, I was freaking freezing, everything went ok on the second take, ehehehehe.