I don't think I would ever restart - maybe replay but once started, just like a ftf game or "real life", you get what you are dealt. I know in the solo plays I have had, I have looked at the board and said "S#!+, that was a bad move..." but then I try to "correct" it and learn from it.
Of course, in FTF, I say that alot more often...
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I am one of those who do feel as if I am "cheating" the other side if I am winning/losing???