In a word, yes. Squishing a ball, skein, or hank of yarn is often the best way for us to judge its texture, softness, "scratch factor," and twist. We all know what our own level of preferred textures is for things that will be worn close to our skin, and we also know that not all yarn feels the same. Some has more loft than others. Some has been treated and blended so that the squish factor is magnified. Some is more raw and retains its natural oils. Some contains blends in certain percentages that give it a truly unique feel. So, no matter how many microns we may be told a fiber contains, squishing it is often the most expedient way for us to judge our softness preference. But, let's return to a moment the question of whether or not you can squish yarn too much. I began this blog post by saying that yes, you can. While fibers tend to be pretty resilient and will bounce back after being knitted or crocheted with, woven, unspun and respun, or plied, you do have to be attentive to the way in which you handle them, or you could inadvertently break the strands or even felt them depending on how rough you handle the yarn. For example, taking a skein and essentially rubbing it repeatedly back and forth over your skin with it to test its softness will cause the spun fibers to create a halo and nearly felt the yarn in question. So rule of thumb: never "scrub" yourself with a skein of yarn unless you want to ruin its structural integrity. Rather, gently squish it or lightly rub it on the back of your hand. Also, continually pulling at a strand or pulling it too hard to test its strength can and often will break it or cause it to lose its stability (which means it may break when you try to use it). Rather, be gentle when testing a yarn's strength. While store policy prohibits people from rubbing yarn against their faces for sanitary purposes, there's no way to prevent people from doing this elsewhere or at home. (Although, really, if you are shopping for yarn somewhere, it's really poor form to rub yarn all over your face.) If you are someone who likes to rub your yarn on your face, you may want to be careful that you aren't wearing any makeup, hair products, or are sweaty because those things could transfer themselves onto the yarn and cause problems with it. There are some who refuse to even wind their yarn hanks before using them because they believe that winding the yarn causes it to lose its natural elasticity. I have not found that, but I would say that overhandling/overusing yarn can impact its springy-ness. For example, let's say that you make something but then after quite awhile decide that you want to do something else with the yarn. Most of the time, the yarn will be fine, but sometimes you may find that because it's been worked over several times that it may not be as lofty as it once was. The bottom line is that, yes, we do love to squish yarn, and part of the fun of picking out yarn is feeling it. But you can do this by being gentle with the yarn so that you don't destroy the best part of it.