I would turn that frustration into a learning experience. One of the tips always mentioned when learning a new detector is ---dig everything for the first 50 hours or so-- . Use the computer we carry between our ears to analyze all of our targets and once it gets enough data, it will start alerting you to differences between trash and treasure.
For example, I've dug many a flattened pop can that showed up as quarters, and like you, dug half way to China to retrieve them. Now, when I get that quarter signal, I mentally go through a quick checklist. Is the signal the right width as I scan over it, is the audio the right volume for the depth it indicates, does the signal get weaker if I lift my coil up a few inches and rescan, etc, etc. All based on 100's of previous quarter digs. Do I still dig deep pop cans? You betcha. Just less of them now ( more based on how much trash I'm willing to dig for that elusive gold which hides behind all VDI's, or whether I'm looking for relics).
One thing to keep in mind is, even with all of the technology used in our metal detectors, it is only telling you what it sees. All it is doing is sending an electromagnetic signal into the ground and because of so many factors (such as size, composition, depth, shape, angles, halos, etc) the induced return signal of some trash happens to be the same as good targets we are looking for.
Until that day when we get machines that can read the date of a coin while in the ground, we are stuck with the computer between our ears to make that final "dig or not dig" decision and only experience can make that easier.
Most importantly, just have fun while out there.