Dwarves will eat just a little bit earlier or later if they see someone eating before or after they do. It's like synchronized fireflies (saw a discovery channel documentary on them). Each firefly watches the a few other firefly's blinks, and slightly tunes the timing of their flash to those ones. Slowly but surely, eventually all of the fireflies are synchronized, and they all flash in unison. It kind of doesn't make sense for all of the dwarves to eat at random times: dwarves should want to eat together. The same could go for sleeping.
Dwarves should use their social abilities far more. While they're on break, while they're eating in a meeting hall, when passing eachother by, etc... This would help to improve the social skill of all your dwarves and keep dwarves just a little bit happier.
Dwarves should go and do something during their break, rather than stand around. They could sit in a dining hall, or in an office, reading the Daily Dwarf, or Dwarf Today. They could actively seek out nice-looking/pleasurable things. They should at least talk to eachother a bit more.
Finally, dwarves should utilize rooms more. A couple getting married? All the friends of those dwarves will sit in the meeting hall, and watch the couple get married. Dwarves could set up plays, play in orchestras (yes, I know I'm getting a little bit carried away here), or hold funerals in mausoleums. It would dwarfanize (humanize) the dwarves, and make social events much more important parts of your fortress. Of course toggling would be nice , e.g. [dwarves are borgs: YES/NO]