Gee, I didn't know that Stephen King's breakthrough novel was rejected 30 times.
Surely it must be part of a massive conspiracy to make big publishing houses seem like a bunch of clowns...?
(The same conspiracy that made so many unsuspecting big publishers make the apparently conscious decision to reject an apparently unsellable manuscript called HARRY POTTER AND THE PHILOSOPHER'S STONE.)
Read the list of 14 bestsellers which were rejected many, many times. And don't give up.
(Thanks to Ashok Banker for the link suggestion.)