I've been working now for a couple of years by splitting my web activity in different firefox profiles. I use one only for gmail, another one for general browsing and some others for spotify and web-based whatsapp.

I do this under the assumption that cookies stored on one profile cannot read the information of different profiles.

Am I fooling myself?

I'm working on a linux machine. This option can be done as well in chrome, but I don't trust chrome.