Have you ever been in the middle of the grocery store when you realized you forgot something in the produce aisle? And then remembered pasta when you got to the dairy section? This is much less likely if you use a list or app that's organized by departments or aisles.
Just as it feels better to work from one end of the store to the other with a plan, it feels better to tackle your to-do list in logical groupings as well. When you organize your to-do list by the type of task, something magical happens. You don't have to use the mental energy switching from task to task. You feel more in control of your time. You might actually enjoy what you're doing because you know you're doing something all the way through.
We use QuickBooks at work. I am in there for budgeting, billing, entering payments, and collecting on past due invoices. It takes a few minutes to log in, so I've started keeping a QB list in my planner. When I go into the program, I can knock out several tasks at once. What I need to do in there is important, but not urgent, so each task can wait until I have a few tasks to do.
When I facilitated a time management program a few weeks ago, a guy in the back of the room shouted, "I hate email!" I shouted back, "Me too!" But I hate it a lot less when I'm in charge of it and it's not in charge of me. I love shutting down email for a few hours at a time at work, and then being really purposeful when I am in my inbox. Just like I keep a QuickBooks list, I'll keep an email list. Sometimes I draft messages in Word so I can send them all at the same time when I log back into my account. When I'm in email mode, focusing on one after another, I'm less likely to get pulled in a different direction.
Today's the 25th of the month, which means tonight I'll be paying bills and balancing our family's checking account. I get paid on the 10th and 25th so I handle most finance-related activities on those two days. I have a folder for each of the days to hold any invoices and other paperwork I receive, and I snooze emails until those days, so I can handle it all at once. It feels great to set aside time twice a month for this, instead of thinking about it daily.
One of the best methods I know to present myself from trying to multi-task (which isn't really multi-tasking at all, but switch-tasking) is to group similar tasks.