You pay a price when you push beyond your comfort zone, and sometimes that price is worth it. When you push that hard, you never really know if it's worth it until after the fact. When and why do you decide to push beyond your comfort zone?
When I'm making that decision, I consider the following elements:
Safety
Will the push compromise safety, and if so, how can I make sure that the push is a safe one.
The affect on others
Sometimes you push beyond your comfort zone to help or support others. If you do this thoughtfully, it can be very positive. If you do it with a "why me" attitude, it may not be positive.
Realistic
You have to be realistic as you push beyond your comfort zone, if you're not realistic, it may backfire.
Buffer the event with quiet, energizing days on either side of the push
You can push beyond your comfort zone now and then, but you have to make sure you have energizing days and time to rest on either side of the push. No one has endless energy.
Onward.