It is true that when we take chances, we stand to lose. But it is also true that we will never win anything if we never even enter the game. Lucky people are aware of the possibility of losing, and indeed they may lose often. But since the chances they take are small, the losses tend to be small. By being willing to accept small losses, they put themselves in position to make large gains.
If you are losing a tug-of-war with a tiger, give him the rope before he gets to your arm. You can always buy a new rope.