Well, panic is by definition unreasonable — by which I mean, it's an emotional reaction rather than a rational one. You're unlikely to make it go away just by telling yourself it's unwarranted, unless you also do something to ameliorate the stressors that are setting it off.

I don't want to push too hard, but I'll add that you don't have to be experiencing a major crisis to make use of a campus counseling center. Universities provide such services in part because they know that being a student can be extraordinarily stressful in and of itself, regardless of the presence or absence of other mental health issues.