Please help,Im fked up

Please answer how?Although I'm an ICSE studenr but This will be a collective help to all the students I recently had my exams and I am a good student seeing the past but these exams were blunders and a stain in my academics In maths exam i did sikky mistake like 12*4=36, Took height common in a question where heights were different and many more In computer idk what happened i missed 2 programs , my brain got blank was not able to reason out ,like it just stopped working and i am losing like max 40 marks

In chem go see the paper and rate it as well on my account , I took mass of Na as 11 despite the correction came to write Na mass as 23 .

So after all this what should be the tips for students who have these issues. PLEASE ANSWER And in this limited time what should I do solve papers or revise or improve in time. Like I'm helpless and I'm going through tough times in mental as well as in my daily life, there is no one to talk to like no one , i don't go to coaching have no activities to do.

Tl;Dr-(gen from chatgpt) I messed up my exams despite being a good student. In math, I made silly mistakes, blanked out on programs in computer, and misread corrections in chemistry. I feel overwhelmed, have no one to talk to, and don’t know if I should solve papers, revise, or work on time management. I’m struggling mentally and need help figuring out what to do next.