I started playing WoT in mid-2013, at a friend's invitation. I played it religiously for years, my satisfaction and fun slowly decreasing, until I ragequit in 2016 and didn't pick it back up until last year. I can see it happening again, but I know how to prevent it this time. How?
PLAY FUN TANKS.
I cannot stress this enough. Most of what I did back then was grind bad tanks to get to good tanks. Once I got a good tank I wanted to keep, I'd file it away as "done" and switch to grinding other bad tanks. As a result, I mostly played bad tanks, which was incredibly frustrating. I suffered through the KV-13 and T-43 to get to the T-54, and then I never played the T-54. When I make a conscious effort to play enjoyable tanks that aren't necessarily leading anywhere–AMX ELC, T-54, SU-100Y, T29, Luchs, and so on–I have much more fun and want much less to drop the stupid thing for another half-decade.
Play fun tanks. Ignore the grind sometimes. It makes this game less of a chore and more of a…you know…game.