I found, after age 40-ish, that my ability to maintain focus on a single goal over long periods had diminished substantially.
So, I made a small tool to help me manage focus. The link (https://github.com/lelanthran/frame/blob/master/docs/FrameIn...) is to a slideshow of how the tool works.
Because how it works is different enough to all the other personal time/issue/task tracker tools that I had used, I recommend reading the slideshow (5-10m reading) before trying it.
I've been using it for a while now; so far it works very well for me. I hope it works very well for you, too.