Say you have ₹20,000 and you cap risk at 2% — ₹400 per trade. A contract is priced at 40, meaning the market implies a 40% chance. You believe the real chance is nearer 55%.
You buy at 40 and decide in advance: exit at 60 if you are right, exit at 30 if the reasoning breaks. Size the position so the move to 30 costs about ₹400, not more. If the spread and fees eat a meaningful slice of the gap between 40 and 60, the trade is not worth taking at all.
That is the whole discipline: an explainable disagreement with the price, a fixed loss, a planned exit, and honest accounting for costs.