This rule applies to all situations where you need to be someplace
at a certain time... give yourself plenty of time and arrive early at
the airport.

That way you are not stressing should everything not go according
to plan or there are delays... such as a long line at TSA.

If you can pack light so much the better... if you can avoid a checked
bag and only have carry-on you save yourself a lot of time and the
potential of a lost bag situation.