Here's a point-by-point response based on the confident approach Aaron teaches. When we first fished he taught me the psychological game based on his hockey experiences. If you keep fishing with an attitude of "I won't catch any," you won't! This one piece of advice had a major impact on my catch rates and totals.
1) Do you move onto another piece of water? YES, in a river like that you know there are high numbers of fish.
2) Do you fish the same stretch again? YES, when conditions change.
3) Do you change flies to fish the same stretch? NO, not usually productive unless you are VASTLY off in size. You should have a good general knowledge of what works in that season and those conditions.
4) Switch to long line or right angle indie rig? NO, unless you feel there is an area of the pool you can't reach with the short line. I have found the long line setup to be more general, i.e. you can short line nymph with the long line setup, but not vice versa. The most general method is using an indicator.
Nothing beats confidence coupled with time on the water.