I read an article recently that used an acronym I had not seen before; T.O.W. Time On the Water. It immediately resonated with me. In a life of fishing and guiding, your time spent on the water is the defining characteristic of your existence. In other spheres they call it field time, and at NASA I imagine they call it space time. It's about immersion to the point of heightened observation. Maybe pure observation.
Nothing makes up for time on the water; no Yeti cooler, no Orvis H3 flyrod, no Hatch reel. Nothing will save your bacon if you haven't put in your days and made the observations necessary to produce in the moment. I have tested this theory and found it to be true time and time again. You can get lucky here and there, and it helps to be fishy, but there is no substitute for having been there before, and acting like it.
On my home water, the Missouri River, life gets easier when you pay attention with your time on the water. Fish tend to rise in the same spots day after day. They like to eat flies presented a certain way more than they care about the fly pattern.
Bugs tend to hatch in the same stretches of the river. They like to do it in rhythms that can be predictable. Other anglers and floaters tend to be predictable too, and finding the elbow room you want for good fishing is usually just a matter of timing and patience.
Tendencies become truths once you've observed them enough times, and then you can make better fishing plans based on them. Of course the most important thing time on the water can teach you is the simplist - nothing is guaranteed, expect the unexpected, prepare for everything and keep logging your time.