Cycle both FD's, at the same time, OFF then ON. Reselect a mode desired. It takes a matter of seconds.
Maybe that works on the 757, I've never flown it, but it won't work on the 737-800. You'll still be in approach mode but a few seconds will have passed. If you fly the NG misd-agin , then that is a great example of how the confusion can begin and why it is important to be able to simply fly the aircraft to where you want it ( which I'm sure you can....I'm not having a dig at you in any way).