Learnt the hard way ....Had an embarassing "chat " with special branch at EGTR a couple of years ago, the fireman at a Channel Islands airport kindly offered to fax my flightplan and GAR to air traffic and promptly forgot. I departed without EGTR expecting me, even though I was flying through jersey zone on an IFR plan. It was completely my fault for not checking, but now I never depart without confirming my destination airport has received confirmation I'm coming and got GAR approval.
LF
Or as Oscar Wilde said "Experience is when you recognize a mistake you've made before !"