It's not really any different than console. Walk into a used games store and you'll be able to pick up a tonne of games at really cheap prices too (probably better than Steam sale prices actually). Unless there's something you really want just don't walk into the store and buying stuff you don't have time to play won't be a problem. I don't even look at Steam sales anymore unless there's a game I really want and then I only look for that.
See, the only reason I go to my local Gamestop is to pick up a preorder and such. Even then I can't impulse buy for $30+ games even with all my Gamestop points. But I come home from work and I've got 50 billion steam deal emails. Then it gets worse with bundles. Which aren't really a thing on consoles anymore.
I'd be surprised if there isn't a way to turn of the steam emails, that could lower your temptation to buy new games that you're not ready to play quite a bit. Maybe even mark them as spam to prevent them from coming through
As for bundles, just don't go to humblebundle etc. In my experience if it's a really good one somebody will post about it on here, so you can still get the good bundles, and that happening is rare enough that you won't constantly be getting tempted to buy them.