Doing just one thing a day sounds like the thing my brain craves. I'm at my best when it's just me versus one task. Two things is usually bearable, several feels overwhelming. I'm not good at multi-tasking, and I don't track time very well, so even when there's plenty of time to do everything, I feel rushed. If I take on two things, what am I going to do if the first thing takes all day? I'm such a perfectionist that I often end up taking ages to do things. And focussing on one thing seems to drive the other out of my head. The other great thing about one task per day is that there's no changeover during the day, my brain has a whole night to rest between jobs. It's so tidy!
But I guess it depends on the size of the task and whether or not it's part of my routine. Small routine tasks don't really count, presumably because they don't need any thought. Just as well or I'd get out of bed and that would be all I could do for the day.
Also, many projects consist of a number of sub-tasks. I'm currently preparing for a difficult journey and I've been having trouble doing it all comfortably. Each sub-task is reasonably small, but none of them are routine things, and they're all rather different from each other, and I've been having a lousy time just trying to pick things to do. A lot of it, e.g. packing, can't really be done until close to departure, otherwise I've packed away stuff I'm going to need. So a lot of it remains undone for good reasons, but that makes me feel bad. I just want to pick up the first task, do it, check it off, next task, till I reach the end, then chill out, but it never works out that way, I get part of a task done and find I can't complete it yet, so I can't neatly check the tasks off, and it looks as if I've done nothing, and I can't easily estimate my progress. Even looking at the task list to try to pick something to do is difficult and somewhat scary. Just shifting my attention from one item to the next seems hard. So I'm only doing one thing, i.e. preparing for a journey, and the steps are all pretty small, but it really challenges my brain to co-ordinate it all. I find myself doing other, easier things, procrastinating and detouring. Everybody else just packs without a whimper.
At work one of my bosses would meet with me once a week and give me a number of jobs to do. He didn't mind if I couldn't complete them all, he just didn't want to give me too little and risk me being idle. I wasn't scared of hard work as such, but the awareness of so many things on my plate would make me feel overwhelmed and confused, and I longed for a system that would tell me of one job and then keep the rest secret from me until I'd completed the first task and asked for the next one. Once I knew about several tasks, I felt I had to immediately start planning my week around them as a whole, which is probably the most efficient way, if the brain can do such a thing. Mine can, but it's hard and it makes me feel anxious.
I guess a lot of the problem is that the Aspie brain doesn't readily flit from idea to idea on demand. It likes to choose one idea and think it through to the end. The only flitting it's likely to do is the uncontrollable analysis of whatever tangents occur to it during that process.