…or maybe just some old-fashioned anxiety & aversion about doing something that is hard work and high-stakes. Not everything that we do less than perfectly is pathological!
another old-fashioned thing that you can deal with more constructively than re-analyzing every aspect of your application time & time again! Next time get up and go do something productive: bake something. Write a postal letter to an older relative who lives far away and would appreciate something in the mail. Clean out the hall closet (quietly). Put on headphones and dance to whatever makes your heart pump. IOW, choose to put that anxiety energy into something positive.
Finally, doubling down on @EyeVeee’s comment about $$. If Brown accepts you, can your parents afford it? Full pay at Brown will be something over $360,000 for your degree, v. UC-B at something around $160,000. If your parents can afford the extra $200,000 without any trouble, happy days. But if you end up having to turn down Brown b/c you can’t afford it, you may well end up resenting UC-B unfairly, just b/c it’s the boy/girl next door that you can afford, instead of being delighted at the opportunity that the 115,000 or so students who are being rejected right now wish they had.