Expect to lose flies. The pictures of the old vest with the used salmon flies make us think of flies as heirlooms. Try thinking of them as bullets. Hunters don't expect to get their bullets back. I have never lost as many flies on a fishing trip to equal the cost of one afternoon of shooting sporting clays.
Flies are expendable.
Trying to save flies and tippet causes anglers to favor water that fish don't favor. If it is easy for you to fish, it would also be easy for ospreys and herons to fish. It takes a few minutes, but it will free you from the worry of running out of packaged leaders from the fly shop. It will also give you time to study the river as you tie the series of knots. I fish a lot better now that I stopped worrying about my store-bought leaders.