It’s dead slow and you feel as though you’ve tried everything in your box. Frantically tying on one fly after the other in a moment of desperation, and you come across a bug that never seems to fail you; a fly that you can tie on without hesitation.
Having such flies is important not only because they clearly have some fish-catching attributes, but you will fish them with confidence. Desperately changing flies every 5 minutes because they clearly aren’t producing can easily work against you. Chances are most of these flies would do the trick if they were given a real trying effort.
Having a fly tied on that you have full confidence in keeps your attention focused on the task at hand. You will let it get down to depth, retrieve it with more intention, and expect that something is going to happen.
For one whole season, I became obsessed with fishing shrimp. I would look forward to the evening session when everybody would leave the lake to go fish the shallows with scuds. After that year, I can almost always tie on a UV Pregnant Shrimp without hesitation. I get a brief replay in my mind of all the times this fly has bailed me out, and fish it with certainty.