Extreme Couponing lesson learned

I worked very hard to match my coupons with sales and had my sales flyers with the items for price matches circled.  There I was at Walmart, my shopping complete.  Three hours of price checking, comparing one ad against another, making sure that I hadn't missed a beat.  My cart was filled beyond capacity.  It is nearly midnight, I am exhausted and anxious.  Had all of my work been worth the effort.  My anxiety builds as I near the register.  I get to the only register with a light on.  I am greeted by the cashier, "Hurry up- It's shift change at midnight."  I tell her I have price matches and coupons and that perhaps I should just wait.  She is hurreling my items across the scanner and she snaps at me.  "No, hurry & we'll get you through!"  Oh my, how unpleasant.  I am doing my best to keep up with her and load all of the bagged items into a seperate cart.  By the time she is done she barks out my total, there are two other employees standing there with her.  I hand her my coupons and remind her that I also have price matches.  "Well, you should have told me that- we need to do those first."  Then they are going through my coupons.  "Next time put your Target coupons with your items also, we need them first, Target doesn't give us money for these."   So I did not get my price matches and therefore I got out of there only saving $9.00.  I was unhappy.  I sat in my car replaying what just happened.  The next morning Kevin asks me how it went.  I told him what happened and he wasn't very happy with the situation either.  I am letting you all know this so that those of you who are going to give this a try will not have to endure this kind of scolding.  Now I need to figure out a strategy to load my cart with price match items at the top or seperate cart, or even a seperate trip.  Some people may be discouraged by this negative outcome.  I am letting it fuel my fire.  I am going to save money, they advertise that they will do price matching so, guess what, next time I will be prepared and they will price match and take every coupon I can find.  Watch out cranky cashier, I will be back, I will be ready for you...will you be ready for me?  This is going to be a better experience next week.