Don't start playing cards to the hand until you know where you intend to develop your tricks. Count each suit one at a time. Both hearts and diamonds have potential for additional tricks beyond the sure tricks indicated. That analysis occurs in Step Three. You will be better served to keep each step separate.
Losers come in two varieties.
SLOW losers are tricks that the defenders must continue to develop before they can be taken as a trick. Count each suit one at a time and count with respect to declarer's hand. That analysis occurs in Step Three. You will be better served to keep each step separate. The most predictable and surest method of developing the additional tricks that you need in order to fulfill your contract.