The Martingale strategy doubles the trade size every time you make a loss (plus a little bit extra), until such a time as you make a winning trade, following which you reset back to the original trade size. The theory is that you can't lose for ever, when eventually you do have a winning trade you will make back all your money.

It works just fine on coin tossing contests, assuming you have an infinite amount of money to bet and there is no limit on bet sizes, but in the real market it isn't practical.

You will never have an infinite amount of money to trade and this method will probably lead to ruin if your system has a tendency to string together quite a few consecutive losing trades.

If your average win size is significantly larger than your average loss size, and you don't typically have many consecutive losing trades this method can work reasonably well, but most of the time this is far too aggressive and in a real market you will in practice over-trade, and possibly lose an enormous amount of money.

This is a method that tends to lead to a high "Risk of Ruin" when you analyse your trading statistics, so it is absolutely essential that if you are gong to use such a technique you be adequately capitalised. You really do need an enormous amount of money to use this technique properly.