(CNN) -- A good mood can make you more fun to be around, and it can improve your health in a variety of ways, big and small.
The Mayo Clinic says optimism not only helps you manage stress, it plays a role in cardiovascular health and even makes you more resistant to the common cold.
According to a small study out of the UK, a positive attitude may also boost the effectiveness of your flu shot.
Researchers with University of Nottingham examined data from 138 people between the ages of 65 and 85.
They all got a dose of the 2014-2015 influenza vaccine.
Scientists took note of several health indicators, like mood, stress levels, negative thoughts, sleep patterns, and diet.
They also looked at antibody responses at four and 16 weeks after they got the jab.
They found that participants who reported a more positive mood also had higher levels of antibodies in their blood.
The study's senior author said there are a variety of factors that can affect how well a vaccine works, but believes the study suggests that mood is one of those factors.
The study was published in the journal Brain, Behavior and Immunity.