For events and appointments, I use a calendar. I also have alarms on my phone to remind me about daily tasks.
For anything beyond that, I do struggle. The best advice I’ve gotten is to pick one thing per day that you want to work on, and work on that. It’s much more productive than task-switching.
I still feel like I add more to my to-do lists than I cross off. I have to periodically review my goals and sometimes I have to let go of something so I’ll have time for all the other things. Chronic pain also limits how much I can do, so that’s part of the problem for me. But focusing on one thing per day has helped a lot.
For apps, I use TickTick. I’ve tried many apps, and this is the one that works best for me personally. I use it both for taking notes as well as for task lists. And I can set reminders on it; I find that this works much better for me than my phone’s default alarm clock and calendar. It also has a feature called “habit” where, for example, I have it remind me to drink water 3 times a day (because I tend to get distracted and forget). On a regular alarm clock, I’d have to make 3 different alarms, which really clutters things up. But on TickTick, it’s just a single entry with 3 reminder times, so it stays uncluttered and makes my life easier.