One of the things that you need to remember in blackjack is why basic strategy exists. It exists so that the player can play each hand in a mathematically correct way. But many of the decisions are losing decisions whatever you do. Sometimes you have to make counter-intuitive plays in blackjack like defensive splitting for example. Let us look at a hand like 8-8 vs a dealer 10 which is 16 vs 10. Now this is a bad situation to be in for the player. Taken from a 52 card deck then we have seen three cards which leave 49 unseen. If we stand on 16 then any 7, 8, 9 10 value card or ace beats us straight away.
There are a total of 10 cards of 7 through to a 9 (we have two eights) and a further 15 ten value cards (the dealer already has a ten) and 4 aces. This means that the dealer will beat our total straight away 29 times out of 49. But they will also pull a combination of smaller cards to make 17 or more as well and so the chance of our standing and winning is small. If we take a card then any card will bust us unless it is an ace through to a five. Whichever way we go then our chances are slim.
But if standing has a certain value, taking a card has a certain value and so does splitting then we take the play with the best value. Quite often this involves placing more money onto the table. If you stand to lose 10% in EV on a $10 bet then you are losing $1 in expected value. However if by splitting your EV becomes -2% then although you now have $20 on the table your EV is only -$0.40 and not $2.
