1. If you really want to avoid GAS, steer clear of review/chat sites that blow subtle differences among bits of equipment out of all proportion to the difference, if any, they're likely to make to the photos you make with them.
2. On a related note - which could, of course, cut both ways - one way of dealing with GAS is (assuming this is an option where you live) to rent the latest expensive toy that everyone is getting excited about. This will satisfy your curiosity, which may be enough - you could easily discover, as I sometimes do, that your reaction is indifference: yes, it's good, but the results aren't appreciably better than what I'm getting now. And, by the time you send it back the initial urge may have passed anyway - yes, this is surely best 35mm 1.4 lens ever, but, frankly, I don't really like how the world looks at 35mm....
3. There's nothing wrong with GAS if you can readily afford it. And it needn't be that expensive. For instance, if you bought a digital body that works well with old manual lenses (i.e., a mirrorless body of some sort - a second-hand m43 with IBIS is a good idea) you could acquire many new lenses to play with that are really cheap and a pleasure to play around with, in part because they're made so well, in part because they can be really good. And while doing all of that you may be distracted from wanting to buy $2000 lenses - especially once you get used to how inexpensive lenses can be....
4. And on a note related to *that*, if you're disciplined and don't keep everything you buy, it's worth remembering that, unlike camera bodies, good lenses don't depreciate much: you won't lose much if you sell an L lens you bought new, and if you bought it second hand in the first place you may even sell it for more than you paid for it. (When I ditched all my Pentax equipment on switching to Canon, the only notable loss was on the camera body; I sold several lenses for more than I paid for them, and they were far from L quality.)
5. You need more lenses.