IS it enough?

When we are not fulfilled we complain and get depressed in life, but when we have a million things going on and tons of activities we seem to feel overwhelmed. When is it enough and how do we know when have actually obtained this happy medium? Maybe we are never really satisfied and that is why humans are constantly looking for other "temptations," challenges, outlets, because maybe we are never really content with just "being." All I know is that emotions are like the weather, for the most part seasonal, but have major waves of both good and bad that always unexpected and usually uninvited.