In fishing, it's really easy to get stuck in a rut. Fishing the same waters, the same spots, and using the same flies might work out relatively well much of the time, but it's always best to have an open mind. Exploring new spots or even venturing to unfamiliar waters is a great way to discover untapped opportunities that may have eluded you. Bass tournaments provide pretty solid evidence of this when an out-of-town angler wallops a guy on his own home waters. That non-local angler came into the situation with a desire to learn and explore—he wasn't stuck "fishing history" as some would say. I know I've been surprised a few times by friends catching fish in areas or in ways I had disregarded or simply wasn't motivated to try. Fishing is a learning sport and nobody truly knows it all!
What I really want to discuss here is that sometimes the "better" or "best" fly is found outside the box—literally meaning it's not in your fly box! It's easy to quickly get stuck on a pattern or patterns that have earned your confidence. You may have hit a favorite body of water once or several times before and absolutely whacked em on a certain fly. Now, when you venture back to that same place you not only have one tied on already, but your box is stocked full of the things. Even if conditions seem similar, the "old familiar" may not always be your best option. It may be a good starting point to see how the fish respond, but if the fish aren't chewing that fly very well it might not mean the fishing is slow—you may just have to experiment a bit.
About five years ago I was fishing along a beach from a flats skiff with an older gentleman I had fished with a few times beforehand. He was pretty new to the local snook fishing and I was helping him to get dialed in. At the time, I had been fly fishing for these critters on the beaches for about twelve years and pretty much had my fly selection whittled down to a single homemade pattern in two sizes. While we had experienced some success, it was generally slow. We were seeing a good amount of snook cruising, but most were totally ignoring our very small and realistic baitfish patterns.
It was around noon, and the other fella started rooting around for something else to try. After a short time, he comes up and shows me his selection—a popper. It wasn't just any popper, but a large, bulky popper in a loud color scheme which I can't exactly recall. I said something along the lines of "yeah give that a shot" thinking it would probably scare the first fish it was thrown at. When a cluster of snook were spotted shortly thereafter, he flung it out in their vicinity and the unthinkable happened—two or three snook immediately went crazy for it! Keep in mind this is around noon, in two feet of crystal clear gulf water, casting at spooky fish that usually feed on things like small minnows. These snook were likely just ticked off and simply reacting to the noisy, gaudy popper, but WOW, it was completely unexpected!
Although the above story is the most drastic example I can recall, there's been countless other occurrences over the years of anglers being successful while throwing something I hadn't considered. A vastly different fly pattern may not be the best solution, either. Sometimes, a simple solution like just trying a new color or size is all it takes to turn the day around or help you catch a few additional fish. It can't hurt to carry along several other styles or patterns just in case your old standbys don't produce as expected. Even if you're pretty certain you have the fish figured out, when picking flies for your next trip always be open to "think outside the fly box" of what you normally use!