You don't have enough sex
Unless you lie perfectly still, most sexual encounters raise the heart rate and blood pressure significantly. Fortunately, studies show that the more frequently you have sex, the lower the risk of heart events. Get busy.
You drink too many sugary beverages
In a massive study of more than 300,000 subjects, more sugary drinks are associated with more strokes and heart attacks. This kind of association study doesn't necessarily prove that your soda habit is killing your heart -- it might be the cigarette and donut you have with it -- but ditch the crap drinks and their friends for your health.
You drink diet soda instead of sugary beverages
Unfortunately, the sugar-free "diet" options aren't much better than their sugar-filled counterparts. Diet drinks probably won't help you lose weight, and they could also do damage to your heart: A study shows that women who drink two or more diet sodas a day have a major increase in heart disease and deaths. Water, unsweetened tea, green juice, and black coffee should be on your list.
You skip medical checkups and don't get advanced lab work
You may be young and "invincible" now, but not even a healthy lifestyle can make you totally immune to heart disease. While lifestyle factors like diet, smoking, and exercise play the biggest roles in heart health, there are genetic factors that are an important minority.