My answer to this might be kinda stupid, but for me it's just accepting the fact that these games ( that get me all hyped up ) are not going anywhere. If I already bought the game, it'll always be in my library, if not I can always get it later. This helps me focus on the games I'm playing right now and I just tell myself that I can always allocate time for these other games later, once I'm done with what I'm playing now.

The thing is you really can't avoid this. There is always something that gets you excited to play a particular game. Sometimes it's a post on patientgamer, or a let's play, a review , it can be anything. And there is nothing wrong with that. After all you are playing games to have fun.

And if you ask me, there is also nothing wrong when you take a break from the games you are currently playing, to play something that you are interested in at that time. But in the end, it's really up to you if you wish to complete the games you are playing first or if you wish to take a break and play something else. These games are not going anywhere, so you allocate the time and resources as per your interest and what you find fun.