To improve in a weak subject, go back to its basics, give it a little time every single day, and practise actively instead of avoiding it. Weak subjects usually stay weak because students avoid them; consistent, basics-first practice is what turns them around.
Find the real gap. Often a subject feels hard because an earlier foundation is missing. If Class 12 maths is hard, the gap may be in Class 10 or 11 basics. Fix the root, do not just push forward.
Study it daily, in small doses. A weak subject improves faster with 30 focused minutes every day than with one long session a week. Daily contact removes the fear and builds steady progress.
Practise actively. For maths and science, solve problems yourself rather than reading solutions. For theory, test your recall. Passive reading rarely fixes a weak subject; doing does.
Get your doubts cleared. Do not let small doubts pile up. Ask a teacher, a friend, or use free online explanations until each concept clicks. Unsolved doubts are what make a subject feel impossible.
Example: A Class 11 student in Surat who feared physics started with Class 9 and 10 basics, solved five problems daily, and cleared doubts weekly. Within two months physics went from his worst subject to an average one.
One practical tip: Change your mindset from I am just bad at this to I have not practised this enough yet. Weakness in a subject is almost always a lack of practice, not a lack of ability.