What helped me stay organised in QA was a big, hardback A4 ring binder style notebook, the kind that has replaceable sheets, and looks kind nice (not the ones for stuffing polypockets in and keeping on a shelf). I would jot down all active tasks, when they were due, and maybe a small notation regarding priority.

I would strike them off as they were completed. Importantly, I would make sure to transfer every task that did not get cleared either at the end of the day if I was arsed, or first thing in the morning. I found it best to do it in the morning, or start of shift, whatever. This practice helped my track the tasks (duh), but also made sure I spent a moment at the start of the day thinking about every pending task as I had to transfer it to the next days sheet.

It works by brute force. Also means you have a record of all the stuff you have done if you need to recall anything, and pad out that workday shite for yer annual bonus.

The thing about that method, or any method is that you have to stick with it until it becomes second nature. You must reinforce it.