the grass is always greener on the other side of the fence

The grass is always greener on the other side of the fence. --.. 这山望着那山高
Too many cooks spoil the broth 人多反误事
You can lead a horse to water,but you can't make him drink... 强求不得
You'll catch more flies with honey than with vinegar.
蜂蜜比醋更能招来苍蝇（奉承比批评更能赢得好感.）