When is the last time you were in an uncomfortable situation? Did you put yourself there or were you forced into it?
You will be forced into these situations no matter what and to be ready for these situations you must constantly put yourself in these situations. When you stretch your comfort zone you are comfortable with a zone that used to be your edge.
There are massive rewards for growing. No longer are you scared of what you once were. You will have more confidence in your abilities. You will be able to gain more leverage and influence.
The pain of not growing leads to massive pain as well. You will always doubt yourself. You will not have new experiences. You will actually begin to go backwards or down because you are not growing.
The contrast between the pain and pleasure of taking action should be enough motivation for you to go out there and reach your goals.