I'm not completely sold on the relationship of stress and heart disease. I spend some time working in politics, and almost all principals worked 18h-days with less than 5h of sleep during the week. Yet life expectancy is higher than average.
There are obviously ots of competing factors at work: they have plenty of opportunities to eat healthy, and the discipline that makes them get up at 5am also makes them go for a run at 5:30. Then again two of my bosses had to retire after run-ins with the crystal meth law they themselves passed...
Considering the limits of willpower, I'd rank it Smoking/Exercise/Food/Sleep/Stress.