One more thought -- start slow. A night or two at a time, until you have the hang of it. We have never boondocked for more than a week at a time -- gotta get groceries and do laundry and dump the tanks. There are extreme boondockers who can go for a very long time without going to a town, but not me.
And if you are wondering how to go a week without dumping the gray water, we often use a bucket to transfer some gray water into the black water tank by dumping it into the toilet. We generate about 5 to 6 gallons of gray water a day (showering and dishes), which will fill the gray tank in 5 days, but we always have lots of extra capacity in our black tank.