Jee Mains is the entrance exam for admission into different engineering courses and to get admission in IITs you need to qualify JEE mains with good marks so as to be eligible for JEE Advance and then you must qualify JEE advance also.
So all i would suggest is that if you are left with only 1 month for the exam, you must stop wasting time unnecessarily and focus on studying and practicing for exam. You should focus on the important topics and chapter of all the three subjects and practice as many questions as possible. Also clarify all the doubts at the earliest. keep solving sample papers and previous year papers on a very regular basis to ensure your performance is upto the mark. All your concepts must be clear and you must study in a synchronised manner. Do not waste your energy and give proper rest to give body and mind. Wake up early and start studying early morning as that is the best time you can understand well. then take some small relaxing breaks in between. Finist up early in the evening do not awake till late night so as to keep your mind fresh.
And at last always remember hardwork never fails. Be confident and you will be able to achieve what you want.
All the best.