ciemnogrodzianin: Just subscribe to HB newsletter?
But honestly there are multiple ways to avoid such situations. Personally I'd recommend IsThereAnyDeal. They allow you to import your wishlist, customize notifications and in my case it works really nice – informing me only about interesting deals and freebies. Removing their emails (~ once a day), when I'm not interested, costs me 1-2 seconds and I guess it just proved to be worth it.
I do all of this but those days I really had it over my head, I was outside home too for days waiting for work related mails and I wasn't in the mental space of checking the promotion folder of my mails or other, but I would have noticed a news post from GOG, because I look at it from my phone to see new releases, should the world end I'd still do that XD
I know it's my "fault" for missing a giveaway but it would have been nice fro GOG to make a news entry or a FB post, instead of 20 CP2077 commercials. But it's ok, really, I just wonder why make a deal with Humble and say nothing on your own site! I hope there's more in the future and Humble GOG keys too like for Steam.