Three Play Guides drills I use when a boss fight turns into panic inputs, including a tiny HUD cover that forces cleaner reads.
Cover the HUD, then earn it back

I do this when I notice I'm staring at bars instead of the boss. Grab a tiny piece of painter's tape (blue 3M is perfect because it peels clean) and cover just one element of your HUD, not the whole screen. Pick the thing you check compulsively: your health bar, your stamina bar, your ammo count, whatever your game makes you babysit. The Play Guides angle here is simple: you are changing the practice environment on purpose, the same way you'd change a drill in a gym. You are not "making it harder" for bragging rights, you're forcing your eyes back onto tells.
Run three attempts like this. No more. If you cover stamina, you have to feel your rhythm again: two swings, pause, reposition, repeat. You'll be shocked how quickly your hands start behaving when your eyes stop hunting for permission. If you cover health, you learn to respect the boss's spacing because you can't bargain with "I can eat one more hit." You either dodge or you don't. There's a weird calm that shows up around attempt two, because the screen stops being a dashboard and turns back into a fight.
After three attempts, peel the tape and do one normal attempt immediately. That "earn it back" attempt is where the transfer happens. You'll still glance at the HUD, but it becomes a quick check instead of a stare. Also, use painter's tape, not duct tape. I tried duct tape once on a cheaper monitor and spent the next ten minutes wiping gummy residue with isopropyl alcohol like an idiot.
The one-minute menu pause that saves your hands

There's a moment in a bad boss session when my thumbs start doing things I didn't approve. Extra rolls. Late blocks. The "please work" button mash. When that starts, I stop trying to brute-force discipline mid-fight and I use a Play Guides trick that feels almost too dumb to matter: I pause in the menu for exactly one minute, hands off the controller. Not scrolling, not reorganizing inventory, not crafting, not checking a build guide. Just pause.
I set a timer on my phone because otherwise a "quick pause" turns into fifteen minutes of doom-scrolling and then I'm cold again. One minute is long enough for your grip to unclench and for that hot, buzzy adrenaline feeling to bleed off. It's also short enough that you don't lose the boss's timing in your head. While it's paused, I do two things only: I roll my shoulders back once, and I take a slow breath in and out. That's it. No pep talk. No "focus" mantra. I'm just getting my hands back.
When the minute ends, I unpause and I spend the first ten seconds doing nothing heroic. I walk. I watch. I let the boss do its opener and I track one specific tell, like the shoulder dip before a sweep or the half-beat delay on the grab. If I can't identify a tell inside those ten seconds, I pause again for another minute and I call it for the night after that attempt. The point is to protect your inputs. Boss progress is great, but not at the cost of training panic timing into your muscle memory.
Try the "ban the punish" round

If you only ever practice a boss while trying to win, you end up "shopping" for damage windows. That's when you take the bait punish and get clipped by the follow-up you swear wasn't there last time. My favorite Play Guides drill for breaking that habit is a single attempt where I ban myself from punishing entirely. No hits. No spells. No chip. You're allowed to dodge, block, sprint, jump, and reposition, and that's it.
This changes what you notice. Without the pressure to cash in every opening, you start hearing the fight. The audio cue that means the second swipe is coming. The footstep cadence that tells you whether the boss is going to slide forward or stop short. The camera behavior when you're too close to a pillar. I play on a normal volume, not muted, because the whole point is to collect sensory info you normally drown out with your own button noise.
Make it concrete: pick one phase (or one move) and say out loud what you're looking for before you walk in. "I'm only watching the left arm." Or, "I'm only tracking the red flash." Talking feels silly, but it keeps your brain from drifting into autopilot. When you die, you should have a single clear note, even if it's just: "The triple slam always pauses before the third." That is a usable note. A blurry vibe is not.
Do not do three of these in a row. One is plenty. The second you go back to a live attempt, your punish choices get cleaner because you aren't guessing. You already saw the end of the animation. You already waited it out once. And yes, it will feel like you're "wasting" an attempt. You're not. You're buying information with an attempt that was going to be a sloppy panic run anyway.