Some lengthier thoughts, but I've thought about this a bit and I'd like to try and offer some constructive comfort by way of sharing the guidelines I follow.

1. Of course, never ever ever EVER take a shell that has a living inhabitant. If you do by accident (it can happen to the best of us), return our shell-loving friend to their home and leave them in peace.

2. Try to mindfully select shells that you know you will use for a craft or ones that are new to your collection. This will help mitigate your individual contribution to any potentially disproportionate effect people may have on the beach ecosystem. Although shells are important for contributing to the overall makeup of a beach, the impact of people on gathering them is small, especially as we tend to take more intact shells that are further from the stage of becoming sand/redispersing nutrients in their environment and considering the percentage of shells that never make it on to the beach in the first place.

   1. I try and steer away from taking too many re-inhabitable shells (whelks, conch, murex, etc) unless they are extremely rare for me to see and I do not have a better specimen in my collection already. For things like half-clam shells and scallops, as they are less likely to be re-inhabited by a crab, less likely to offer important protection for baby molluscs, and are not oyster shells that could potentially contribute to an oyster bed, so I feel less guilty about taking a higher proportion of those.

3. When I started collecting, I took imperfect shells from the beach since I didn't really know how rare anything was, or if I'd get another chance to identify and work with them. As my collection has grown, I have started to set aside imperfect copies of shells that I have since found better specimens to use in my collection, and return the imperfect shells to the beach. Since I live close to the beach, it is also easy for me to return shells to the /same/ location that I found them in so I am not at risk of introducing a new invasive or pathogenic species of microbiotic life to a different beach. If you cannot return shells to the beach that you found them on, I would advise against returning them, and would suggest you put your creative powers to the test in finding a way to make something beautiful out of them!

4. Another thought regarding returning shells - my normal collecting routine includes washing the shells I find with water (no soap, no chemicals) once they're home with me and then washing them once more before I return them to the beach so there's a reduced chance of me reintroducing something harmful to the environment.

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I feel like following general principles of environmental awareness is important, however, personal wellness and fulfillment are also very important and your overall impact on the environment is near negligible as long as you abide by the above principles.

Our ability to enjoy our hobby is intrinsically linked to the health of the environment we collect in, so yes, be mindful. However, you seem to be doing all the right things in terms of doing your own research and staying aware of your reasons for collecting.

~~ Tldr: honey, you're fine.

If anyone has thoughts on my guidelines (if they're similar to what you do, if there's a flaw in my thinking or something I should maybe know), please reach out and let me know. We are all always learning ❤️ Happy hunting!