Sometimes we are our biggest critiques. We strive for excellence but when we fall short, sometimes, our own thoughts and feelings are much harsher than our peers. Being a perfectionist is a blessing and a curse. You always strive for success but when you fall short of your goal you undermine everything that you may have already accomplished. I can attest to this firsthand.
A normal level of self-criticism is good, it keeps you grounded. However, too much pressure can lead to self-loathing and the overall lowering of one's self-esteem. A lot of college and high school students are under a lot of pressure from their course loads but the added stress caused by oneself isn't helping. For my fellow peers, I urge you to remember to ease up on yourself and take the time to see that you won't be judged as harshly by others for most of the time.
Stress already comes with life. It's part of the territory. If you are really hard on yourself, then that usually means you produce quality work or you have a strong work ethic. Know your worth. It's okay to fail but dwelling on your mistakes won't allow you to reflect and produce something more incredible. Tame the knit-picky beast within and I guarantee you will come out on top.