My "pen"(Round Thirteen For Sarah)

When motivated, I extend my pen To reveal if I can endure the test. It retracts, when it needs to take a rest, After I am done expressing my sin. My pen is able to make women grin, And helps me get the stress off of my chest. Desired by my most critical guest, It is the envy of average men. In the beginning, my pen did not lack, And continued to get better with age. So, my pen has always been welcomed back, Because my pen has become all the rage. Although my ink is not, my pen is black, With a unique way for filling a page.