I've a notes.txt file that follows me around in most jobs I do. It's more a journal than a planner. Sometimes I put TODO in, sometimes what to do when a change needs to be implemented so I don't forget. That works quite well as I can return to that later, or see what I was doing some months ago. It's in vim, which works well too for me as I'm already familiar with how to edit.

One of the popular getting things done methods was to keep your stuff in one place, at least this article keeps inline with that idea.

If it works, keep doing it.