This is a major concern for patients and practitioners alike. While the allure of facial perfection can drive some to endlessly seek unnecessary filler, skilled injectors know when to draw a line in the sand. If you are with a provider you trust, allow them to recommend volumes or frequency of treatments. Surgeons tend to be the most skilled and knowledgeable injectors and I recommend seeing one over other injectors in general, especially in terms of their professional opinion about what is right for you. It's also very important to have a well-defined goal when seeking facial injections (or any plastic surgery, really) so that your expectations are in line with your results. You should know what you want and know what to anticipate, so that "perfection" is not so abstract. The perfect result is the one you want to have, it isn't defined by how voluminous your cheeks or lips are. Find balance between the excitement of fillers and your aesthetic goals, and you will not have so much to worry about. It's important to remember that fillers are best used to accent and contour the face, smooth wrinkles and fill lines, and these are subtle changes to the face. If you are seeking a greater or more permanent change, you might consider surgery or as an alternative to dermal fillers.