Why?
It might be true that he has maths background
If he understood math he would know he is playing a -EV game. He got lucky, but he will wipe out his luck by keeping tl gamble.
On a much smaller level, I made the same mistake that I hope nakowa will make eventually: I didn't stop playing when I was ahead.
I mean, you shouldn't play a -EV game at all, technically, but say you did and you made a profit. Now you're *still* looking at a -EV game, so the advice to not play *still* holds :P
The only difference is that, if you were lucky enough to have made the irrational, but profitable choice to play (and won), then you could actually leave the game with a profit if you leave now.
For me, that profit was +100% of my initial bet. For nakowa it was much higher, both in absolute and relative terms. In the end, I started one martingale too much, and the profit was all gone. For nakowa, because his initial winnings were much much higher, it'll take longer to be eaten away. But there's a real chance he won't stop either before it's all gone.