Ha, I thought this thread was about like careful as in deciding what to wear, which I am just a complete URGH at.
But OMG I am really not careful with my clothes - I go to art college for christ sake - and seeing as there literally is no other place to show off clothes (apart from maybe like town on a saturday....), I had this really nice suede-feel light grey jacket from John Lewis and I loved it and I wore it one day and someone got red acrylic paint on the very back of it. Then my nan tried to get it off with like some weirdo cleaning crap and it just made a mark that looked like a bruise, ha. It wouldn't fit now anyway.
I destroyed several shirts last year actually *it all comes back*
Several YSL and Ralph Lauren shirts got their cuffs dyed with procian dyes - permanent deliberately for dying clothes.
A cream silk shirt got completely destroyed as it got paint on it, I took it off to clean it and put it down in more paint, and more paint, and more paint. It's now a cleaning rag.
I'm really not careful with my treasured clothes :S