first quarter reflection, need some advice

hey guys! so finals did not go the way i hoped they would, especially for this one class i worked to have an A in all semester and then the final took it down a letter grade. i feel so bad and disappointed with myself because i did try and study so hard for it. i just froze during the final. im a first year by the way. i knew it would be hard, and i know it's normal to get a b here, but i feel so so so bad. i also want to go to grad school and i just feel so demotivated. do you guys have any tips to get past this, any advice as well? i thought i would take harder classes to challenge myself, but it's really hard to stop tying my self worth to grades.