Welcome to the forums and to your new adventure!
Everyone forgets something... and brings more than they will ever use! Each time we go camping as I pack for the next trip, I take out stuff I haven't used... makes the Airstream a bit roomier and lighter!
Some folks pack everything and take it out each time, or seasonally... depends on where you live. Out here in California I only remove stuff that might freeze in the winter [liquids] and the rest of the trailer is usually stocked ready to go ~ one trip to the market, check the closet for seasonal jackets and we are ready to roll! Also depends if you cook in your trailer or eat out a lot....
Give it a try, if you need something KeithC is right, there is always a Wal-mart somewhere closer than you think!
Mrs. NorCal Bambi (traveling in S Tardis)