No I don't think so, this is something ive experienced in many games since I was little. My theory is this, you get into a boss battle, you don't know what's happening, you're acting on instinct, then you get to a tricky last part and die.

You load back up, you're still full of adrenaline, you're reeling from what happened. Your lizard brain is fighting with your human brain in a battle of control vs strategy and you're overthinking tactics, which dont mesh well with the beginning part of the fight.

You continue this cycle a few more times until you can finally just do the first part on pure practice and focus the actual strategy on the last part. A few more deaths there to apply it correctly and youve beaten the boss