What's the biggest cause of health problems today? Stress, right? So why would we do ANYTHING stressful if we can avoid it.
Often, the only thing stressful about a cruise is getting to the ship on time.
For us, that's a no-brainer. We go early.
What's "early"?
If you're inclined to be stressed about being late, probably a couple of days. We always try to get to the embarkation city the day before the ship leaves. A night in a hotel is a small price to pay for peace of mind. If it's a more exotic (i.e., distant) port, we try to be there 48 hours before the ship leaves.
Airlines are sometimes delayed for weather or mechanical reasons. As everyone knows, they're not obliged to do much in the way of compensation, especially concerning a future leg of your journey. Insurance is an option, but not always a solution.
We read recently about a couple that missed a ship departure when the airline changed to a smaller plane and bumped them. They received what they felt was insufficient compensation and caught up with their cruise two days later. It was stressful, to be sure.
Finding a cab to take you from a hotel to a ship is not.

Carnival Destiny
5 nights
September 17, 2012
Miami (return): Grand Turk, Half Moon Cay, Nassau
Inside: $329
Cost per day: $65
www.carnival.com