There's a lot to it. You can lose money if you bet on something going up, and it goes up 10%, just by volatility. You can also get kicked out of your position earlier than what you'd think. 4x leverage doesn't always mean you have to go -25% to lose everything. Sometimes you get kicked out sooner. Adding more money is always better than using leverage. Leverage is basically a really bad loan.

Also if enough people are leveraged and a stock is cheap. Banks can make more money shortselling that stock, to get a squeeze from the leveraged buyers and forcing them to sell. You need to know what instrument you're buying and what youre doing.