Doubling your position size after every loss guarantees that a long enough losing streak — which will eventually happen — wipes out the account, no matter how small the starting bet.
The Martingale System
Launch
18th century (roulette)
Death / Exploit
Ongoing
Total Loss
Varies — often 100%
A losing streak of even 8-10 trades in a row, which isn't statistically rare, requires an exponentially larger position each time — most accounts run out of margin long before the streak ends.