I used to be the same and it drove me nuts. Eventually I looked for a solution and ended up installing Limit Tabs[0] to limit the number of my tabs[1] to 10-15. I couldn't be happier!

[0]: https://addons.mozilla.org/en-US/firefox/addon/rudolf-fernan...

[1]: On my desktop. Unfortunately, the extension is not available for Firefox for Android, so on mobile I tell Firefox to discard tabs that I haven't used for a day.