The “negativity bias” is a well-recognized psychological phenomenon: our brains react to the bad more strongly than to the good.
When our thoughts wander, we'll end up brooding; the negativity bias also means that anxious, angry thoughts or memories grab our attention more consistently than happier or pleasant thoughts.
To find out what this means for your relationships
According to research on the negativity bias, it takes a ratio of 5 positives to make up 1 negative in a relationship. Studies show that a marriage is more likely to be stable over time if there are 5 times as much positive feeling and interaction between the spouses as negative experience or feeling.
The negativity bias is why one weird or angry exhange can dog you all day, no matter your partner might have cuddled you later, washed the dishes, and walked the dog: two shy. But seriously, while the research indicates that ratio is an aggregate, over the duration of a relationship and not a single day, it's something to keep in mind when possible; the days turn into years.
The research is very specific about the ratio, too, as there can be both too few and too many positive experiences -- too many may indicate a lack of healthy conflict, openness, and difference. Of course, the negativity bias doesn't pertain only to romantic relationships; there are indications that work relationships, family and friendships may depend on this ratio for their stability and health.