Quoting bearisgray: "it is better to be further away from the edge than too close to edge."
Very true. What I usually do is stop stitching, pull the quilt out from under the presser foot and leave tails about 4" long when cutting the threads. When I turn the binding up at a 45 degree angle, if the edges of the binding don't quite line up with the edge of the quilt sandwich, I thread the bobbin thread through a big-eye needle, insert it from underneath through all the layers at the exact point when the stitching should have ended, and tie it off with the needle thread. This is so much easier than correcting stitching that went too far.