Time warp

I have adult-onset ADD. No, I'm not clinically diagnosed or medicated, but I definitely have focus problems. It hasn't always been this way. But, now that I'm a parent and full-time worker and wife and soccer carpooler and owner of a pet with allergies, I'm always running in several mental directions at once.
Except...
Except when I'm being creative.
Does this happen to you, too? When I sit down to write or create or develop concepts, it's like I fall through a portal and am gone from our dimension. An hour can pass in a blink. I can forget to eat or pick up my kids. If not for the alarms I set on my phone, there's a fair chance night would fall without me noticing.
So, what's the deal? From what I've read and people I've talked to, this is creative Zen. This is meditative immersion, minus the lotus position. You can get so swept along in the flow of your own creativity that you literally check out of reality for a while. You're surfing your own brainwaves, dude.
I'm not suggesting this is some kind of trance or psychotic break. I'm saying that it's what athletes and high-performers call The Zone. Being in it is awwwsome. Stuff is clicking. Puzzle pieces are snapping into place. The picture is laser sharp.
Now, there are times when I sit down to write and I literally can't get a subject and verb to agree. My ideas are flat. My stamina is nil. I often say it's at these times that my muse in on vacation. But, when she's with me and full of energy, there's just no telling what we'll come up with.
I'd love to hear your stories of being in the zone. Do share!