SHORT ANSWER
Losses yes. Big losses - no you don’t
This assumes you’re trading a live account, funded with your own money or, possibly, your broker’s money. Some spread betting companies in the U.K. have introductory offers whereby they will fund your account to the tune of £100 or so.
Paper trade for free
The even better news is that you don’t have to accept any losses at all if you start by paper trading on a simulated trading platform. (Most brokers offer this facility.) As a rule of thumb, if you can’t make a paper profit, then you’ve got less than no chance of making a real profit trading a live account. Only switch to trading live when you’re able to make a consistent paper profit and you’re comfortable with both your trading platform and your trading methodology.
Beware of paper profits
There is a flip side to all this good news though which explains - in part at least - why some traders experience heavy losses early on. While paper trading, few of us can resist the temptation to fantasize that we’ve got the pockets of George Soros along with his Midas touch. The result is that we might make 500% profit or more in a single day. This is entirely doable when paper trading. The mistake would be to think you can repeat such a feat trading live with real money. You might do it once. You might even do several times after that. But sooner or later – your luck WILL run out – and you’ll blow your entire account. The moral of the tale is to only paper trade with the same position size (i.e. same number of shares or contracts) using the same stops as you would do if you were trading a live account, funded with your own hard earned cash.