The only productivity hack that i found useful is:

Having a unintrupped time in working flow.

This concept can be applied to any other activity as well as formal working hours. Whether it's Lifting some weights in GYM or Reading an interesting book or even spending quality time with a someone you care about.

Ask yourself: When was the last time you had three or even four completely uninterrupted hours to yourself and your work?

Mayble it depends on the kind of work that you do, But uninterrupted time is the single best thing for quality output and genuine enjoyment that i found; for almost anything.

Anything more than that, feels like an efficiency trap.

That's it.