We've all seen it happen: finding the motivation to actually make it to 6 a.m. boot-camp with a friend; nailing the last round of squats when you see those around you powering through; or pushing ...

Naps help Constance Kobylarz Wilde, 58, recharge, especially if she takes them right after lunch. Wilde, a marketing manager and health blogger in Mountain View, Calif., is constantly juggling her ...