Excited...yet a little annoyed

By all estimations we have got the house...we agreed on terms, we had a great inspection, we got an approval from our lender, we've submitted all the necessary docs that they need, we've put down earnest money, we have a projected closing date of March 17-we already have the stinking truck scheduled to move! Everything seems to be in order...right? Well, I have my doubts and I'll tell you why... the way I always understood buying a house-you get the "Final" approval for the loan BEFORE you order the appraisal....am I wrong? Apparently so! To my surprise, we have to getting the appraisal by Thursday and only THEN will our docs, application, appraisal, etc.. FINALLY go to the underwriters to get the FINAL approval-which can take another 3 days....we may not even really know for another week if we have actually gotten the house or not!! Now I am flipping out-I have felt sure of this house from the moment I walked in to it so I know I just need to have faith, but it's REALLY hard when I know that something could still go wrong! Oh my heck-I am so nervous! Anyone...I need advice/comfort.... help!!!