For example someone reads about a crystal like yellow calcite that it's great for the mind, energetic, amplifier, positive. If you're already wired to being productive and/or just living a good healthy life, then the crystal might amplify all of these. However if you are all over the place, tired, priorities out of order, stressed and so on, then you think adding a crystal like this might turn things into positive things however the crystal is merely carrying a specific frequency and in its nature it is very neutral, therefore it can amplify your being all over the place with priorities out of order, it can make you energetic in the sense of making you have thoughts to keep pushing when instead your body wants to take it slower and recover to restabilize. A crystal can do more harm than good sometimes and by now we should all keep this mind, most of the times the crystal will help and having intention is good, though what I am trying to say is that using a crystal does not always equate guaranteed positive change and help, sometimes it just won't help you the way you think it would. In other words, using the same crystal in two different mindsets can result in two total different experiences, leaving us with a burning thought, maybe when we judge a crystal for its energy, perhaps we are judging instead the interaction of our energy (and current mindset) with its energy, so if something works for you now it might not work for you later and vice versa, and also if something works for someone else or doesn't, it doesn't mean it will apply to you as well. Might not make much sense for every scenario though, but it's a good thing to keep in mind. It's good to discuss about how to use crystals in a smart way and not to ignore this subject because of the desire of 'all crystals are good' - they are neutral and don't want to do anything as they are rocks, however when you tap into their energies that's when things start happening. To wrap this up, if I build my own momentum of productive things, build a routine around healthy lifestyle and work discipline and quality relax time etc, then adding a yellow calcite for example will improve my entire momentum. If however I am in no momentum except the one of procrastination and what not, then adding a yellow calcite will actually amplify the procrastination and get me even better at current things I would be doing, even if those things would be deemed as negative and attributed to what a crystal would 'do'.
Take all with a grain of salt of course