If you have travel insurance from any company, (including Princess) it would depend on what is covered in the policy. If you just decide not to go, the insurance probably wouldn't pay.
If you think there's a chance that a family member (or you) may become ill and you'll need to cancel, be sure that's covered. If you're concerned about missing the ship in a port, be sure the insurance covers that possibility.
You really just need to find a travel insurance policy that fits your needs.
Personally, I would never buy the cruise line's insurance. In the very unlikely chance that the line goes "under" there's a chance you'd lose everything.
"A truly happy person is one who can enjoy the scenery on a detour."
Carnival Inspiration 2002 Carnival Elation 2004
Grand Princess 2004 NCL Sun 2005
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Caribbean Princess 2007 NCL Dawn 2008
Island Princess 2008 Island Princess 2009
Golden Princess 2009 Carnival Conquest 2010
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Carnival Dream 2012 Island Princess 2013
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Sea Princess 2014