There are two reasons to be nice to others: it's good for them, and it's good for you. It really doesn't matter which reason grabs you more. Either way, what matters is your behavior -- and not just to others, but more importantly for you.
Life simply goes easier for people who behave well. The cynics among us might clamor that this is counterintuitive. Okay, now consider this.
Are you interested in improving your daily experience? Would you prefer a kinder, gentler, and yes, fairer, environment at home or work?
Right. Me, too. Ha! So much for cynicism.
There are two ways to look at reality: either it's you against the world (which implies that somehow you are separate from everything and everyone), or you are part of the world (in which case your experience is affected by others, and theirs by you).
Aside from being illogical, it's no fun to be separate from the world. Humans are social animals. We need one another, and we thrive on companionship. Frequently fighting with others to protect yourself takes a lot of energy. And unless your survival is at stake, that energy could be more constructively funneled into other ventures. This isn't to say that fights don't happen, or that self-defense isn't useful. It's a question of habit, and outlook, and overall investment of energy.
If you're part of the world, as I believe we all are, then we're interconnected. Your reality affects mine, even if we have no direct personal connection. You're reading my words. I'm writing for you, without knowing exactly who you are. We share the planet, and this lifetime, and during these few minutes we are considering the same thoughts.
We're different, and yet we have a bond. This coexistence enriches my life, and yours, presumably, since you are taking valuable time to peruse this blog. Surfing the web may be one of the most impersonal ways to get personal with others, but even so, the process still works. And the code of behavior, for example here on The Huffington Post, contributes to and facilitates our community discussions.
The social code of behavior (i.e., the golden rule, etc.) likewise facilitates face-to-face interaction. This morning, I received a human greeting from my bank's customer service representative (nice, especially after the automated greeting that came first). She said "Hello" and asked, "How are you?" I replied, "Fine thanks, and you?" From there, the discussion was easy. I told her about my situation, and she did what needed doing. This conventional interchange worked: my banking needs were met, and so too were our human needs.
Now think about the waitress at the local diner or the checkout person at the supermarket. Although interactions with such people are inherently transactional, how we approach them is discretionary. Yet our approach contributes directly to the outcomes. If you snarl at the waitress, she might deliver your food cold. If you make eye contact and smile at the checkout person, she might return the smile, and smiling feels good. What's true with strangers applies even more powerfully with friends, colleagues and family.
These little interactions matter, and cumulatively, the tenor of our exchanges with others influences the quality of our daily experience. Lots of little niceties can make a "good day." Lots of cranky or negative interchanges lead to feeling drained and cynical. Either way, we get used to what we experience, and our familiarity somewhat predicts the future.
The brain is amazing; it changes throughout our lives in response both to external and internal stimuli. Getting bumped hard on the head alters your brain, as does healing fully from that impact. Being chronically stressed out changes your brain, as does purposefully calming the mind. As a result, the more stressed we are, the more normal stress seems to us. The more we practice self-calming, the greater our resilience. It's the same with happiness, and, alternatively, it's the same with anger.
Playing nice with others is so important precisely because external and internal events alter the pathways within the brain. It's also why doing makes life easier -- for you and for them. The nicer we play, the more familiar we become with playing nice, and the more we benefit from the constructive outcomes associated with playing nice. The more normal such interactions become for everyone involved, the more frequent they're likely to occur.
There's that old saying, "The gift is in the giving." True enough, and playing nice is the gift that keeps on giving. When we care for others, we gain the pleasure of connecting, and we sow the seeds for receiving care in return. What we do matters, and the joy of life is yours, and mine.