My first ever business trip a couple of years ago and also my third ever flight. I had only ever been to Zante before that...
About 1.5 hours into my 3 hour taxi journey to Heathrow do I realise I forgot my passport.
Calling and calling, trying to wake my parents up as it's 6:30am and hoping they can drive it down to LHR. Manage to board the plane in time my parents arrived 20 minutes before take off, luckily I had been in constant communication with the airline so they were very supportive
I spent 3 weeks in Bogota with 3 t-shirts and 2 pairs of trousers.
Lesson learnt? quadruple check your passport and wallet are with you.
Oh and I still get mocked for it 3 years later