Calm and Centered's R states:

R Commit 1 foundation: After your opponent plays an attack, discard all cards in your card pool.

If my opponent plays an attack as a block, if I react with Calm and Centered, would my attack even reach the damage step and calculate any damage, or would it be considered an aborted attack at the block step?

As soon as your attack leaves the card pool it "stops', so it would not deal dmg.

However if they were going to fully block and you had a full card pool it still could be usefull to clear your pool.

Actually, no, the attack would still deal damage at this point (at least under the current TR), specifically because of 302.8.3.4:

302.8.3 The Block Step: In the block step, the defender decides whether or not to block the attack. In order to block the defender must choose a card with the appropriate block symbol. A high zone attack may have high or mid zone blocks played against it. A mid zone attack may have any block zone played against it. A low zone attack may have low or mid zone blocks played against it. The difficulty of a block is figured by taking the speed of the attack that the defender is blocking, adding the block modifier (the +X number inside the block symbol) of the block, and then adding one for each card in the defender’s card pool. If the defender fails to play the block, their block is placed in the discard pile immediately and they may not attempt to block again. Once a block is played the attack is blocked, this is the effect of a card that is played as a block. If the zone of the block matches the zone of the attack, that attack is completely blocked. If the zone of the block doesn’t match the zone of the attack, that attack is partially blocked.
302.8.3.1 When the defender attempts to play a block they must adhere to the normal resource symbol restriction (Reversal of previous rule).
302.8.3.2 Cards that trigger off of playing a block will only trigger if the card is played as a block during this step. EG: You may not respond to “Playing a Block” when attacking with a card that has a block printed on it. A card being played as a block, even if it's an action card, isn't played for the ability on the card that is played as a block.
302.8.3.3 Effects that change the zone of a block after it has been played will not make the block illegal.
302.8.3.4 If an attack is discarded from the card pool during this step it will still deal its damage during the Damage Step as normal.

I don't think so Smazzurco

You have up to the Enhance phase to discard an attack from the card pool to abort it. Past that point, it will resolve and deal damage.

So calm and centered used on an attack block will make the present attack still deal damage ( if that was the case ) and resolve fully.

EDIT : ninjaed by Aslum...

I thought once an attack left the card pool it (and its effects) immediately ceased.

I guess this is only true during the enhance phase (see Make a Difference)

Thanks for clearing me up

*STAMP* for aslum

attacks can only be aborted during the enhance step.

I don't remember the exact card, but I'm pretty sure there is a way to abort an attack BEFORE the enhance step.

ok, then to be more clear - the last chance to abort an attack is during the enhance step.

discarding the attack at any time before the block step will abort it.