If you're just a big kid in an adult's body, we have good news for you.
A new study suggests that feeling young at heart can actually help you live longer.
On the other hand, people who grumble about being past their prime may be heading for an early grave.
Researchers from University College London analysed data from a study on ageing which monitored the progress of 6,489 people for more than eight years.
Although participants had an average age of 65.8, most saw themselves as being younger than they were.
Just under 70% felt three or more years younger than their actual age, while 25.6% had a self-perceived age close to their real age.
Another 4.8% felt more than a year older than their chronological age.
During the 99 month follow-up period, 14.3% of participants who felt younger died compared with 18.5% of those who felt their actual age, and 24.6% of individuals who felt old for their age.
Writing in the journal Jama Internal Medicine, authors Isla Rippon and Andrew Steptoe conclude: "The mechanisms underlying these associations merit further investigation.
"Possibilities include a broader set of health behaviours than we measured (such as maintaining a healthy weight and adherence to medical advice), and greater resilience, sense of mastery and will to live among those who feel younger than their age.
"Self-perceived age has the potential to change, so interventions may be possible. Individuals who feel older than their actual age could be targeted with health messages promoting positive health behaviours and attitudes toward ageing."
The research showed a strong association between self-perceived age and cardiovascular, or heart and artery, health.
However, there was no similar link between self-perceived age and death from cancer.