Our emotions are infectious but positive emotions are much stronger than negative ones, that's the conclusion of a recent study that followed 4,700 people for 20 years published recently in BMJ, a British medical journal. One person's happiness can affect another's for up to a year too so it's not simply a fleeting ripple through social circles.
It's interesting that proximity is such a major factor in our responses. For example we need a friend who lives close to us for greater affect. The greater the distance the lower the impact. It's also fascinating that we apparently have social filters because a neighbor we see rarely can have more impact on our emotions that co-workers that we see every day.
So next time you're sad, it may just be the people you're hanging around with! Find happy people and you'll be happy too!