How do you time manage and prioritize your work and projects?

I have, within the context of my job, things to do that will take various lengths of time and are of various priorities. If I get blocked on one it'd be useful to know what to switch to, and on.

I have, within the context of my personal life, things that I want to do that will take undetermined amounts of time and are of various priorities.

It'd also be nice to have a record to go back and reflect on when I did what. And it'd be nice to plan a little ahead so that I can decide what I hope to do next.

So... how do you do it? I am so bad at time management. Is there a useful software I can use (if so, is it foss)? Is there a way to keep consistent with my planner so that I don't fall behind on managing my time management, without falling into the trap of spending much effort on creating a time management system that all my time is spent managing my time.

Send help :(