Melissa, an ESL teacher and textbook writer in Vancouver, never meant to fall in love with her credit cards. When she signed up for her first one in university, scooping up a free MP3 player in the process, she hardly gave it a thought. What was one card with a $500 limit? Surely she could handle that.

And she did. For the next five or six years, as Melissa's credit limit rose to $1,000, then $3,000, and eventually hit $7,000, she paid her purchases in full each month and mentally patted herself on the back for her fiscally reliable ways. She was even on the road to hacking down her condo's mortgage and paying off her student loan.

But then, slowly, without even realizing it, Melissa started loosening up with her spending. Her best friend suddenly decided to get married down in Aruba and Melissa threw the wedding expenses, resort fees, and plane ticket on a new card she'd signed up for that offered travel points. Then an inspection revealed her condo's underground parking lot needed crucial structural repairs. The price tag? Over $8,000 for her share of the construction costs.

She ran out and applied for a line of credit to pay for it.

Soon Melissa found herself signing up for store credit cards, swept up by the promise of saving 20 percent off her new sofa or 30 percent off a winter jacket. And when envelopes began pouring in from credit card companies offering low introductory rates if she moved her current balance to them, she took advantage of ...

Get Chatelaine Earn Spend Save: The savvy guide to a richer, smarter, debt-free life now with O’Reilly online learning.

O’Reilly members experience live online training, plus books, videos, and digital content from 200+ publishers.