Actually Xu Shen's rationalizations are not so much worse than yours:
It has to be admitted that neither explanation is particularly compelling or enlightening for the modern reader. As a learning crutch, how about these:
爿 a stick, a chip, a small piece of wood; I carve it to so it takes the 狀 shape of a 犬 dog.
The 水 water is like my 兄 brother; under these 況 conditions I thrive.
Another way to deal with recalcitrant characters is to just accept oneself's mnemonic ineptitude and to proceed reading and writing. Chances are that the more important items will show up often enough that they will become familiar enough sooner or later. It must be said that some things will never feel at home in the minds of some learners, and still cause a burden in terms of time spent and maybe wasted. Perfection is a noble goal, but determination to attain it without any lacunae is a certain way to failure; sometimes the way to learn something depends on getting over not being able to and going on with whatever comes up next. We cannot always explain, attain, or keep everything. Even Confucius, when discussing why 犬 is used to write dog, once remarked: "the ancient dogs must have looked strange indeed".