No strategy wins every time. What separates those who survive from those who blow their account is not being right more often, but losing little when wrong. Here are the basic risk management rules, with numbers.
Risk a small, fixed percentage
Many traders risk between 0.5% and 2% of their balance per trade. It is not a magic rule, but it has a mathematical reason: at 1% risk, ten losses in a row cut your account by about 9.6%. At 5% risk, those same ten losses leave you about 40% down.
Remember too that losses are asymmetric: after losing 40% you need to gain 66.7% to get back to where you started.
Think in R multiples
Call R what you risk on a trade. Losing your stop is −1R; winning twice what you risked is +2R. Measuring in R lets you compare trades of different sizes and understand your performance independent of balance.
Set daily and weekly limits
Decide in advance how much you are willing to lose in a day (for example 3R or 3% of the account) and stop trading when you reach it. The worst decisions are usually made right after a losing streak, when trying to win it back.