No, you should not have to prepare your own report. I discourage this practice as asking an individual to write his or her own evaluation report may give the Soldier the impression that the report is not a priority to the chain of command. I would, however, encourage you to write your own report if your rating chain has asked you to do so, as you are in the best position to describe your achievements.
Ideally, rating chains should ask the evaluated Soldier for input to ensure a complete report. I would encourage leaders to solicit such input from Soldiers that they rate, but to write the evaluation themselves. This shows your Soldier that you care.