Stretching your boundaries can be a good thing.  If you are living your life and feel comfortable as if there is nice sizable protective bubble around you, then perhaps it is time to begin to step beyond your comfort zone.  We do the most growth in our lives when we reach towards things that we at first felt were unattainable, yet, later feel accomplished that we were able to achieve.  In the same context I believe that it is very similar to exercising.  At first you don't want to do it and then when you begin you feel somewhat uncomfortable and finally when you finish you are filled with endorphins that make you feel more energized.  With exercise it is being consistent that allows you to begin to like that feeling of energy and that then the positive hormones which are released in your body are an added plus.  In life, we can operate in the same manner.  If you have made plans to go back to school, learn a new trade, begin a new health regimen or perhaps follow something that you feel passionate about, then you should begin walking towards it.  One step at a time adds up to a full journey.  When you begin to feel discomfort, remember that you will feel better soon, because you are stretching your mind, body and spirit.  Just like exercise, you will build a tolerance for and surpass any discomposure you may feel.  Soon enough you will realize that you are far beyond any apprehension may have had and your goal is within your grasp.  Remember that the more we unfold the more of ourselves we become.