Random Number Generation, or RNG, is a highly debated topic in almost every competitive video game genre.

However, it still exists in subtle ways that can completely alter the outcome of a very close match.
Starting Hands and Card Rotation
Your starting hand is entirely random, which can immediately put you at a massive disadvantage against an aggressive opening.

Professional players build their decks specifically to minimize the chances of a truly unplayable starting hand.
Balance your average elixir cost.Don't panic if your starting hand is bad.Accept that sometimes you will lose to a lucky start. The Unpredictable AI
Sometimes a unit will retarget unexpectedly due to a micro-movement by another troop, completely ruining your defensive setup.

To counter this, veterans always place defensive buildings in exactly the same specific tiles to guarantee consistent pulls.
Genre TypeRandomness ImpactDrafting GamesLuck is the primary factor in individual matchesStandard Tower RushMatches are decided by placement, timing, and resource tracking Embracing the Chaos
Getting angry at a bad starting hand only causes you to make further mistakes and lose the match entirely.

Focus on improving your timing and placement, and let the RNG sort itself out in the long run.