One of the couples climbing the Gros Piton with us in St. Lucia is also celebrating their 10-year anniversary, like my husband and I are. As we hoist our tired muscles up and over rocks and natural mountain-made stairs, our guide (who is younger than all of us by a decade or so) asks us what the secret is to making it through 10 years of marriage. The four of us chuckle and reply, “Hard …