I'm notorious for laying out my yoga mat, dragging over my weights, and knocking out a 30-minute cardio routine at 11 p.m. However, this pesky habit could be wreaking havoc on my sleep quality. "Try to work out in the morning or early in the evening," Andrew Stiehm, MD, sleep specialist with the United Lung and Sleep Clinic in St. Paul, MN, told me in an interview for POPSUGAR. "Exercise is wonderful, but it's also stimulating. The exhaustion you feel isn't sleepiness. In fact, getting good sleep can actually be harder."