I think it is best if viewed as a challenge rather than an obstacle. A Topic forces the writer to step outside his bounds and really come up with a new way of tackling certain subjects. I have written all sorts of oddball verses well outside my comfort zone and each has made me a better and more well rounded writer in the end.
Sticking to topics you like and writing the same damn verse week to week in a different order and with a can of paint over it isn't the best way forth if one intends to improve.
For example, this week I am doing my legwork in watching the film "V for Vendetta" and taking notes so that I might better serve the topic. This is not my typical "thing" and it requires a good bit of time and effort but in the end if it produces a superior product I am happy to invest. I think being assigned a topic or choosing topics from a pool are both solid mechanisms though assignment reeaaally forces you to dig deep at times.
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