This tiny script keeps my gmail inbox clean and manageable.
It auto-archives any emails older than 2 days (you can change this obviously) unless they're starred - this changes my email experience in two ways:
1) My email inbox ONLY has emails that are either new or that I decided were relevant. I have two days to notice this.
2) When I'm scanning my email, if I see something important that I don't have time to deal with, I can star it and keep moving and know that it'll still be visible and in a manageable-size queue later.
When I travel off-grid it is a bit of a pain since I have to go through a lot of archives, but that can be addressed by just turning it off.
I also ruthlessly unsubscribe to things I've stopped reading to keep everything manageable.