To the OP, I can understand this on multiple levels. I don't have an SO, but I get incredibly jealous and insecure when I think my friends in the department are better than me. It's terrible for all of us, and I need to fix it. Jealousy and comparison are very, very destructive to any relationship. You already recognize that, and you know you need to change. I don't have the answer for you not that one, but it is a problem worth working to fix.
Also, psych. Sigh. During my interview day at a highly ranked program, two of the professors commended me for making it this far in the application process as an undergrad. I was ultimately denied because I am a 21-year-old undergrad and they had master's students competing for the same spot. My POI was incredibly nice about it, expressed interest in my future, and even said she hopes I'll consider being her post-doc several years from now. My undergrad advisor is only 9 years older than me and she was amazed by how much more difficult admissions have become. I don't know what kind of psych you're going for, but if it's clinical, you can't take anything personally. Clinical psychology Ph.D. programs are now more competitive than med school.