So many good ideas presented; I have not read them all yet so I apologize if I am repeating someone else's idea. Well, remember that expensive equipment can be rented from lensrentals.com so if you only need the big glass for specific vacation trips or whatever, no need to own it, just rent it! If you end up renting the same piece of glass like 3 times, then consider purchasing it. As to what piece of glass to own, only the OP can really know what that is for them. I would recommend going back to basics when feeling creatively blocked. Go out and use a mid focal range lens on a walk around shoot and note what length comes up most on the EXIF of the pics. Get a prime in or near that length and only shoot with it for 1 - 3 months. See if your creative juices start to flow again once your mind is freed from thinking about the equipment like if you should have "the other lens" on the body.
Good luck on finding your mojo!