He who is brave is free.
Years ago, my grandfather was diagnosed with lymphoma. In addition to that, people in my family suffered from hypertension, high cholesterol, diabetes, depression, anxiety, addictions, and many had a very hard time controlling their weight. But lymphoma was the last straw: I didn’t want to develop a chronic illness, so I decided to tackle things upstream and start taking better care of my health.
I thought that I’d just been dealt a pair of bad genes; no one in my family smoked or used drugs. We didn’t sit around all day eating. So our genes were causing all of these things to happen—right? Wasn’t that why so many people in my family developed chronic illnesses at a certain age?
When everyone around you is doing the same thing, it seems normal—but that doesn’t make it healthy.
A few years ago, researchers at Caltech asked a group of students to rate various t-shirt designs. Afterwards, the students were informed what other groups thought of the shirts: fellow students at Caltech and sex offenders. When asked what they thought of these groups on a scale of 1 to 14, subjects rated their fellow students at Caltech positively (9.23), and were less enthralled with the group of humans known as sex offenders (1.85).
Learning about other people’s opinions changed how the students rated the t-shirt designs: they aligned themselves and their scores with fellow students, and fled from anything resembling a link between themselves and the guy with the creepy white van.
As social creatures, we’re influenced by other people—but we’re very selective about who we actually learn from.
Finding out that you disagree with people you care about is aversive; agreeing with others whose opinions you care about actually makes things more rewarding. Think about it: if you all like the same song, “Baby Got Back” can become something greater than my song or your song: it becomes our song.
Other people in our lives have the power to turn the subjective into objective reality.
When we agree with others we like, it’s easy to get carried away with how right we are—how objectively awesome our food, hobbies, decisions, and lifestyle choices are. Sharing dessert with a loved one tastes better than shoving cake into your mouth alone in front of the fridge; this is scientific fact.
The more you agree with someone, the more you see the world through the same set of values, opinions, and beliefs; you lack perspective on where your views lie on the overall spectrum. When everyone around you is eating the same way that you are, it seems normal—regardless of whether or not it’s healthy.
 Keise Izuma and Ralph Adolphs. “Social Manipulation of Preference in the Human Brain.” Neuron 78 (2013): 563–573.
 Daniel K. Campbell-Meiklejohn et al. “How the Opinion of Others Affects Our Valuation of Objects.” Current Biology 20 (2010): 1165–1170. Jean-François Gariépy et al. “Social Learning in Humans and Other Animals.” Frontiers in Neuroscience 8, no. 58 (2014): doi: 10.3389/fnins.2014.00058.
 cf. C.D. Hardin and E. Tory Higgins. “Shared Reality: How Social Verification Makes the Subjective Objective,” in Handbook of Motivation and Cognition, edited by R. M. Sorrentino and E. Tory Higgins. (New York, NY: Guilford Press, 1996): 28–84.