how can u b sure?

hi everyone..
i am new here n i have a question
since most of u r very good writers n poets
how one can know that he have that thing inside..meaning,,
if u r a good writer would u know it?
how can u b sure of that..is there a way..
mayb by ur friends' comments or opinions but wat if they r not enough..do u believe them when they say.."well that was good"
do u trust their judgement..or do u trust urself?
i am not a real writer,but sometimes an idea crosses my mind n i find myslef writing about it..
wat do i need 2 improve myself(common question i know!)
well that makes 2 questions..
any replies?