Diana Jackson just walked 2,192 miles. The 23-year-old Darien resident is among 3,300 people each year who try to walk the entire length of the Appalachian Trail, from Georgia to Maine. But she’s one of the 25 percent of them who complete the task. She learned to hike with her parents in the White Mountains of New Hampshire. When she was 7, announced her goal of making the entire trek.