What puts me in the zone is the problem I am working on. Just thinking about it for a couple of minutes and I'm in.

Same here. I can almost say it becomes somewhat of a problem to keep a normal day schedule. It takes 2 minutes and I'm gone for at least 12 hours.

It happens about 3-4 out of 5 times just because I real like the software I'm building or because I get thrilled about how to make something 'boring' a masterpiece to look at or even because I know there is something I don't understand.

It's almost like a drug to keep coding en digging deeper every day. To a point where I even feel somekind of a huge pressure in the middle of night to 'profit' very hard of the last minutes i' m awake.

Doesn't feel healthy anymore haha. But I just love to much somehow

Then there's pills to help getting you there.