I could fill a couple of really boring books with all the dumb things I did in the first few years after 'discovering' that i could actually trade on betfair.

My biggest single loss ever wasn't on horses though (although when on tilt a couple of times blew my entire bankroll in a single afternoon of racing) but on the T20 World Cup cricket when England played West Indies. I had a very substantial initial wager on England, quadrupled it at the end of the England innings and then even added more after Windies lost early wickets at some stupidly low price. I am embarrassed to say that I left it all out there...didn't even bother to eliminate my liability and then watched it evaporate in the last over.

I look at that now and cringe......sheer greed and arrogance and probably a desperate need to recoup losses on some 'system' that I was staking 15-20% of my bankroll on after a few successful trades.