Imposed restrictions are all about removing common treads so you have to think outside of the box. Writing a poem in a certain meter is certainly challenging,

Imposed restrictions are all about removing common treads so you have to think outside of the box. Writing a poem in a certain meter is certainly challenging, but not the same thing as writing a poem where you can't use the letter `e'. This isn't about self imposed restrictions, but merely a choice to do something the hard way.