When the customer service agent told me she'd applied the points and my balance was now $0, I was tickled. Zero. As in, cruise paid in full. As in, I'd just knocked off my final payment without spending a single additional dollar out of pocket. Here's the thing: I wasn't trying to be a rewards genius. I wasn't obsessively optimizing every spending category. I just signed up for a credit card when a new one launched, used it to pay my cruise like I was going to pay anyway, and