User blog comment:Yxz2014/Possible big plot hole??/@comment-79.173.233.163-20141001170242

i think they mean by " clear objective" is Eren acknowledging why he needs to transform to a titan. without him knowing that he is a titan, it won't work.

my guess for it working the first time could be because Eren with his state of mind thought of something like: "if i was as big as they're i would kill them all" which unintentionally made him acknowledge why he needs to transform, it's far fetched but that is my two cents.