Fully endorse the remove stress policy promoted above. Even though I'm only 1 and a quarter hours away (by car) from the airport I aim to arrive 2.5 hrs (3 if long haul) prior to departure. If any problems crop up on the roads/motorways (and they have on the odd occasion), I have a panic-free 60 min buffer available and a mild-panic
30 minute reserve. Once at the airport I go find myself a quiet corner and catch up on my reading.