how does Critical thinking affects my writing

Answer 1

If you do not think critically -- and think well -- then your writing will undoubtedly be very repetitive, uninteresting, uninformative, etc.

http://en.wikipedia.org/wiki/Critical_Thinking
Read the second paragraph especially.

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Answer 2

Check this site, especially the part under "The Result."

(Broken Link Removed)

Answer 3

Critical thinking is one of the most important skills that you will learn in school. These sites will give you some insight into the positive effects.

http://www.canberra.edu.au/studyskills/learning/critical

http://infotrac.thomsonlearning.com/infowrite/wr_critthink.htm

http://www.nwrel.org/scpd/sirs/6/cu11.html

http://www.media-awareness.ca/english/resources/educational/teaching_backgrounders/media_literacy/aspects_critical_thinking_1.cfm