I have a Cowboy 4500 I got last year, never used a sewing machine before and learned everything I know so far from this forum and experimentation and screw ups.
that said, I'll admit as I'm sewing in the back of my mind I'm always praying everything goes good and the stitching flows seamlessly till I'm done. obviously this corner business happens to everyone and the way I've been dealing with it is go real slow approaching that corner, if it looks like it's going to overshoot i bring the needle up then raise the foot slightly and move the work piece back by hand while lowering the needle by manually turning the flywheel, when it looks good hit the pedal and drop it home...then slowly bring the needle half to two thirds back up to make sure it catches the bobbin thread...
then make the turn out of the corner and continue on. one thing I'll add, shortly after I got my machine I removed the little brake pad in the servo motor. that brake won't allow you to turn the flywheel by hand unless you press on the go pedal a short distance, which I found to be REALLY short between releasing the brake and the motor running.