remorse is common. but don't overdo.
which lender is this, BOA? did they take your contract before appraisal? do u know what I mean? your offer was their reference. otherwise, how could it be exactly the same?
I am not sure how hot this property is, which tells how much room to negotiate. I had same situation before and went right ahead to close the deal. it really depends on each individual.
good luck!