thing you can do to prevent a stroke

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 Lower blood pressure

High blood pressure is a huge factor, doubling or even quadrupling your stroke risk if it is not controlled. "High blood pressure is the biggest contributor to the risk of stroke in both men and women," Dr. Rost says. "Monitoring blood pressure and, if it is elevated, treating it, is probably the biggest difference women can make to their vascular health."

Your ideal goal: Maintain a blood pressure of less than 120/80. But for some, a less aggressive goal (such as 140/90) may be more appropriate.

How to achieve it:

    Reduce the salt in your diet to no more than 1,500 milligrams a day (about a half teaspoon).
    Avoid high-cholesterol foods, such as burgers, cheese, and ice cream.
    Eat 4 to 5 cups of fruits and vegetables every day, one serving of fish two to three times a week, and several daily servings of whole grains and low-fat dairy.
    Get more exercise — at least 30 minutes of activity a day, and more, if possible.
    Quit smoking, if you smoke.

If needed, take blood pressure medicines.
Source
http://www.health.harvard.edu/womens-health/8-things-you-can-do-to-prevent-a-stroke