I was a dental hygienist for 32 years and I am very aware of washing my hands, not touching my face, etc, very, very aware. We wore N95 when ever around others, ate outside or on our balcony, etc.
On our 30 day last September, I will even be bold enough to say that I was literally one of the best "covid avoiders" on board. But, our whole hall had tables about a week before the cruise ended(notes from the captain saying about high covid rates, etc) and I did put up a sign for the room steward not to enter (they still did unfortunately) and I think that is how we got covid on the last day of the cruise. It was so hard to think we had literally done everything possible and still got covid.