It's no secret that poor sleep gets in the way of all kinds of good things in life. 

People who drive on too little sleep -- and there are a lot of us -- are more likely to be in accidents that result in injuries than people who've had enough rest.  When we haven't slept well, we make lousy food choices and have trouble metabolizing our food. 

Staying up too late studying actually hurts high-schoolers' academic performance.  Among the younger set, slight decreases in sleep make kids more likely to act out.  A team of faux astronauts suffered a variety of sleep disturbances over the course of a 17-month simulated Mars mission. A 2011 study in the journal Sleep linked sleep quality to feelings of social connectedness -- suggesting that health problems associated with perceived isolation and loneliness may have a lot to do with how well we sleep.

Over the weekend, a team of researchers from UC Berkeley said it was exploring yet another way that lack of sleep may affect us: by making it harder for us to appreciate our loved ones.

Psychology doctoral student Amie Gordon spoke Saturday about three studies she's conducting at a meeting of the Society for Personality and Social Psychology in New Orleans.  In the first study, 56 undergraduates were asked to assess their previous night's sleep; some of them were further asked to write up to five things for which they were grateful and then report how thankful or grateful they felt at that moment.  (It's known that people who experience gratitude are happier, healthier and better connected to those around them.) People who had slept well reported feeling more grateful after making their lists than people who had slept poorly.

In the second study, 69 undergraduates in relationships recorded their sleep and their feelings of gratitude for two weeks.  Each night, they recorded how well they had slept, how appreciative they were feeling, and whether they were feeling selfish or "able to be there for their partner" if he or she was in need.  Poor sleep was associated with reduced gratitude and increased selfishness.

A third test indicated that members of 71 heterosexual couples felt less grateful toward their romantic partners if either person had slept poorly.

"You may have slept like a baby, but if your partner didn't, you'll probably both end up grouchy," Gordon said in a statement.

She said this may be because poor sleep makes people more selfish and less capable of putting their partners' needs above their own.