http://rachota.sourceforge.net/en/index.html
Here are a few offline, desktop applications. The first two are personal task organizers, but have more features than Google Tasks. The second one also has a feature for keeping track of time spent per task.
I personally like Zim, which is like a tiny personal wiki application. It is not designed specifically for task lists, but I have definitely used it for that. It's simpler than the other two, and I think it's possible to use with only a keyboard if you learn the key-bindings.
Yep, you really can't lose, especially if you properly frame the best and worst case outcomes.
BTW, as an aspiring independent worker myself, I recommend you start using some sort of time-tracking app to time yourself when you're working. It's a lot easier to focus on work stuff and not goof off when you know you're "on the clock" -- even if you're working for yourself. I use Rachota and like it quite a bit, but I know there are other alternatives.