Storm Mechanics

I'm building an Izzet Storm Commander deck with [[Prismari, the Inspiration]] as my commander. Prismari gives all of my instants and sorceries Storm.

My question is, am I obliged to use every copy I create of a spell? The most concrete example I can think of is with [[Counterspell]]. Let's say I have Prismari on the board, an opponent casts their first spell in a turn, and I cast Counterspell at instant speed. Based on Storm, I would have two copies of Counterspell (the original + one copy). Am I obligated to play that second copy? If so, and nothing else is on the stack, then my two copies of Counterspell would just cancel each other out, wouldn't they? Does that mean I can only effectively use Counterspell when the Storm count is on an odd number? Or can I just have one copy of Counterspell fizzle off into the distance?