k i have noticed this allooooot of times!
that i can never draw good on a blank paper n i m amazing when i draw in my text books!
just what the heck is that all bout?
if u notice (which u cant cuz u haven't seen my text books) i draw good in my photocopied text books, for example in my english text book i drew this portrait of a guy on which we did a character sketch for me it would mean both ways personally and physically hehe
then again, last year i used to draw on my photocopied social text books, arabic txt book n now on my pass papers too (its a pic of this really cute girl :3 with anime eyes n hair but the rest is all of natural person that is her lips n nose)

then there is one more thing i have heard alot of ppl said to me
that ppl who have long finger draw well, (n that i have long fingers n my bro too O_o)
then those who can curve their toes r good in dancin
umm i dunno if these things are actually true