You should lie down straight on bed, close eyes, breath deeply. Concentrate from head to toe. 10- 15 mins in the morning or evening
Do pranayama - close one nostril, breath from one side and then release from other nostril.
Self suggestions - imagine you are in exam hall and all the questions are easy and you are writing very well. Do this daily till exam
Next Steps
Whenever u feel frustratiion while studies, try to divert your mind e.g. count 50 to 1 backwards while taking deep breath