It is difficult to back up a full-sized trailer. My advice is to practice with an open trailer where you can easily see the back of the trailer and how it is reacting to your steering input. Rent an open trailer from U-Haul, the longer the trailer the better. Practice until you are good at it, and can put the trailer anywhere you want while backing.
Then practice with your travel trailer. You need mirrors that extend out past the trailer, with conex mirrors of both side of the tow vehicle, so that you can easily view both ends of the trailer.
A tip that helped me is that when backing in a curve, make sure the radius of the curve is on the driver's side. That way, you can also just look out the window, or easily step outside to monitor the process.
Good Luck!
Bruce