Assume an important client in a distant city has scheduled a meeting with her lead attorney at 1:00 pm a few days from now.  She asks you to attend since it involves a final decision on your recent proposal.  You need to be there.

You check the airlines and find a flight that gets there by 10:00 am.

Uh, oh!  You planned no wiggle room!  Possible consequence?  The flight is seriously late, or worse, cancelled.

It may work for you that it’s not your fault the flight was delayed or canceled, but not for those awaiting your participation.

Sometimes you're the only one who suffers, e.g., you're attending a seminar that covers an important topic.  You might be missed, but you haven't destroyed the meeting for other participants.  Try that with the client in this example, and you've not only hurt your chance to influence the decision (and develop a relationship with the adviser), you've seriously inconvenienced your client.  Not good!

It's tempting with a busy career or special family events to cut it close.  Sometimes it's unavoidable -- like a meeting scheduled on very short notice, but other than that, give yourself some wiggle room, and don’t plan on taking flights or long drives the day of an important meeting.