You play 100 rounds of a coin flipping game where you win \$2 for a head and lose \$1 for a tail on each round. Clearly since the coin tosses are independent the expected winnings are \$50.
Now, suppose you play at most 100 rounds of this game as before, but this time you stop early if you accumulated \$50 of losses. How does this change the expected winnings?
Naively one would think that this "stop-loss" reduces the losses leading to higher expected winnings compared to the first game, but this does not take into account scenarios where we subsequently recover from the losses: for example the stop-loss throws away the profitable scenario where we throw 50 tails followed by 50 heads ending with positive winnings of \$50.