Early on in life, I learned two basic lessons from my father:
Better be 30 minutes early than 1 minute late (numbers may vary, but you understand the principle)
Be nice to people. Say hello and smile - even if you don't know them.
He probably had his reasons for developing that method of operation, and overall, as many children do, I guess I accepted this as "If dad says so..."
I mentioned the reasoning to "tuning" your behaviour in a previous post, so I won't elaborate on #2.
But a few words on #1... Better be very early than a little late.
It's a good habit that forces you to plan ahead (usually, a good thing), not to arrive breathless and/or sweaty (usually, a good thing), and - once you got this habit in place - it allows you to spend your time and energy focused on your real goal - instead of making your goal to be on time...
Just Be on Time. And if you can't be on time - be Early.