Do you believe that a cheerful disposition keeps you healthy?

I do believe in that. As Patch Adams once said "Laughter is the Best Medicine"! and it is just very synonymous with having a cheerful disposition in life. our body just responds on what we have invested and ingested. i believe that your friends who have had diseases were some of those who got sick (regardless of their being cheerful) with other underlying medical problems. goiter is a result of imbalance in our thyroid hormones or could be deficiency from our dietary intake of iodine. sleep apnea occurs when one sleeps with a full stomach or in case that a person gain so much weight, unless otherwise if she is inborn to have larger tonsils or tongue, small airway structure, etc. cancer happens with a lot of risk factors (familial tendency, sedentary lifestyle, inappropriate diet, exposure to chemicals and other environmental factors). but, there are also some medical conditions that respond well with having a cheerful disposition by limiting the attacks of stress and anxiety thereby keeping a person both physically and mentally healthy.

As far as everyday illnesses go I think there is definitely some worth in this. If you think about people who are easily stressed they tend to get worked up by little things and spend a lot of time worrying. If you're stressed or worrying when you go to bed you tend to not get enough sleep, or don't get good quality sleep which can leave you feeling run down. This can then effect your immune system allowing all those nasty little bugs to just wander in. In contrast, people that can just brush life's annoyances off tend to be a lot more relaxed and cope better with stress. I think that when you're happier there are higher instances of certain hormones in your system, which can help to boost your immune system.