"The Comfort Zone" is a dangerous place. Sure, it's comfortable, but it's also The Land of the Average. Look, there are enough people in that group already to take care of its business; they don't need your help.
The issue at hand is that the comfort zone doesn't make for change. If you want everything to remain the same, then continuing to do what is comfortable and not challenging yourself makes sense. The problem is, you will either lead change or change will happen to you. When change happens to you, it is most often change that you have no control over and change you don't want. In fact, it's usually a "happens" that can be lumped into that wonderful phrase, "Sh*t happens."
The comfort zone can be illustrated perfectly with the difference between recreation and training. If you are out for recreation, you are basically in the comfort zone, just enjoying the swim/bike/run with no specific goal in mind. If you are training, then you are pushing yourself to reach a goal.
You cannot improve yourself without pushing past the boundaries of your comfort zone. Luckily, you can use the comfort zone as a tool to improve yourself. It's simple - Just ask yourself if you are going at a pace that: 1. Everybody else would be going at if just out for a recreational jaunt and would put you in the middle of the pack. Or 2. One that would put you at the lead of the pack so others are following you. If you answered the former instead of the latter, you should know that you will continue to get the same results you have always gotten. Not exactly productive use of your "training time", huh?
It's that slight difference that you can apply 24/7 in all your endeavours. It also happens to be the difference that puts you in charge of change instead of change happening to you. It's not a huge change in pace, by the way. It's only ever so slight, but it makes all the difference in the world.