Every time your heart beats, it pushes blood, nutrients, and oxygen through your arteries to reach the rest of your body. But when you have high blood pressure, it's a sign that your heart is having to work too hard to pump that blood where it needs to go. The result: Damaged arteries, a worn-out heart, and an increased risk of heart disease—which is to blame for the deaths of one in three women every year. Here's what causes high blood pressure, and how you can fight whatever might be throwing your heart into overdrive.