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

It just means that man is never content with what he has. Sometimes we are blessed with all the good things in life but instead of being grateful for such blessings, we're always looking for better things, eventhough what we have is usually as good as it gets.

Well here is a common example people who are single wish they were married and married couples wish they were single again.

Another one girls who have straight hair want wavy hair and girls who have wavy hair want straight hair.

It is a common psychology and we can not change this feeling. It is born with the human beings to compare themselves with others. They are never satisfied with what they have and always think of what others have is better. This has spoiled many personal lives.

When it comes to social life, there may not be a bigger evil than this mentality. If people can divert these feelings to a much positive side and achieve things which will be useful to the society, then OK. But this always does not happen. Much of the suicide, due to financial crisis at personal level has their roots in this greener fence effect.

I think it means that you always think that things can be better than what you already have in your life by looking elsewhere. And that is not always the case, sometimes you just don't realize how great things are in your own life.