Freelancers: how much of your week never makes it onto an invoice?

I'm a freelance 3D/motion designer in Bern, and for years my honest answer was: more than I wanted to admit.

Not the big blocks — those I remembered. It was the ten minutes of client email, the quick After Effects fix before dinner, the revision on a Friday evening. By Sunday I'd be scrolling file timestamps trying to reconstruct my own week, and all the small stuff was already gone.

I eventually got tired enough to build my own fix, which launches here tomorrow. But I've never met a freelancer who has this fully solved, so I'm genuinely curious how others handle it.

Do you track time as you work, or reconstruct it afterwards?

If you use a timer app, what made it actually stick? Every one I tried died within two weeks because I forgot to press start.

And have you ever worked out what the unbilled time costs you per month? I stopped counting once it passed a full day.

Curious how you've solved it — including if the honest answer is that you haven't.