I've had 10 minutes trying to reverse a trailer between some cones and have to admit to being an abject failure. I'm sure with practice I could be just about competent, but it plays havoc with your brain (mine, anyway).
It seems impossible at first but if you keep at it it will just click and you will wonder what was so difficult at the start. Short trailers, especially those that where the distance between tow hitch and axle is shorter than the wheelbase of the tow vehicle are nasty little so-and-sos; longer trailers are easier to control.
Agree entirely with Jonquirk and Angus. Could put a boat trailer with a GP 14 dinghy and wheels at the very back anywhere I wanted, no problem. But a 6' x 4' full of camping gear would jackknife on me before I got to the h in "Oh s**t"!