This might sound stupid, but the hardest thing I found about riding fixes was not the coasting thing - it was getting my second foot into the freaking pedal! It turns out I lock in with the left foot, push off and then COAST to get the right foot locked in. This IS NOT an option on a fixed gear, so I had to play a game of tag with the right pedal (while trying not to fall down or hit something) until I got secured. It was d@mn humiliating when I started, but I got better over time and can now ride the simplest bike out there. Realizing the stopping is different can be scary as well, but it only took me one time to figure that out.