We all have that one friend who is sarcastic and irritable by nature.
But while you might find your friend funny, there are now concerns people with hostile traits such as sarcasm are putting their heart in danger, research suggests.
A study of nearly 2,300 heart attack survivors found those with "hostile traits" such as sarcasm, cynicism, resentment, impatience or irritability were at greater risk of dying of a second heart attack within the next two years.
Researchers also believe the emotional state of always being negative puts a strain on health.
The researchers, from the University of Tennessee, tracked 2,321 heart attack survivors, conducting a personality test that tracked the patients for a 24-month period.
At the end of the two years, the participants' survival rates were compared to their personality scores, and hostility could be accurately used to predict someone's chance of dying of a repeat heart attack.
The researchers, writing in the European Journal of Cardiovascular Nursing, said "someone's character could impact the heart through both behavioural and psychological mechanisms.
"Hostile individuals have increased clotting times, higher adrenaline levels, above-normal cholesterol and triglyceride levels, and increased cardiac reactivity," they said.
"These known inflammatory factors may initiate cardiac events and increase poor clinical outcomes."
People with a positive outlook also exercise more, eat better and are less likely to consume alcohol.
Being optimistic also reduces stress and anxiety hormones, which can raise blood pressure and place a burden on the heart.
Study author Tracey Vitori of the University of Tennessee, Knoxville, said: "Hostility is a personality trait that includes being sarcastic, cynical, resentful, impatient or irritable.
"It's not just a one-off occurrence but characterises how a person interacts with people.
"We know that taking control of lifestyle habits improves the outlook for heart attack patients and our study suggests that improving hostile behaviours could also be a positive move."