To me, there’s concentration and there’s flow state. Concentration is more of a manual process where I intentionally ignore distracting events. It involves building a structure that can hold up to bumps and it’s hard work. Flow state is a groove where distractions melt away and only the task remains. One can turn into the other, and and depending on how your brain works they can both be fragile.

The background noise feels muted, movements are much more precise, you start easily making intuitive connections between concepts. If I’m moving around to get something done, it’s like someone else is controlling my movements while I’m already planning my next steps.

Time is weird. You’re thinking and doing stuff faster than normal but at the end of the day you’ve spent more time working than you realised.

I love the feeling, unfortunately it takes a deadline to get there.

You lose track of your senses, and notion of time. A complicated knot you try to untangle from all angles, is all that remains.

“It’s a lot later than I thought it was. At least I got a decent amount done.”

Opposite direction: “Crap, it’s a lot later than I thought it was. I wish I had gotten more done. Maybe I’m not cut out for this.”

As @Tahl_eN@lemmy.world said in another comment, there’s concentration and there’s flow (aka the zone).

Concentrating takes effort, is often tiring, and requires disipline to block out distractions. It can feel good to consentrate on a problem or task, give it all your mental energy, and achieve your goal. It can be a fragile state though. If a distraction does break through it can completely disrupt your thought processes, causing you to lose track of everything you had in mind, and effectively sending you back to square one. Practice helps avoid that, but concentration is inherently mentally taxing.

Flow is different. You will probably only reach it through concentration, and may not jnitally be aware of the transition, but you’ll know it afterwards. The complex becomes simple, stuctures untangle themselves at a thought, you feel mental clarity unlike any other time, everything you’d been struggling with becomes effortless, and time ceases to have any importance. It’s more like a trance or meditation than a normal mental state, and you can stay in that state until your body physically runs out of energy. I’ve ended up sitting at my desk for nearly 24 hours without rising, and without eating or drinking, utterly engrosed in the task at hand, not noticing the sun setting and rising again, and felt entirely calm and rested at the end of it.

Concentrating feels tiring. It feels like I’m actively trying to shove something into my little toddler brain.

Distracted feels like I haven’t slept in awhile but I’m not tired. But everything holds equal attention. Husband asking a question is the same as the cat waking by and needing to be told she is a lovely cat is the same as my phone sending an alert is the same as the TV playing an ad I hate and need to mute the TV and what was husband asking again?