I used a D800E for 4 years [had been using cropped sensors for years prior], and in that time some very nice FX lenses. But recently sold it all off and bought a Fuji XT-1 and a couple of lenses. I had the same issue, I had all this wonderful gear, gathering dust .... it had become a chore to just go shoot! Since I got the Fuji I'm much more relaxed about my photography, I feel my creative juices flowing again. It's no more about the gear, but about me!
I'm back to being the hobbyist I enjoyed before I ever tried to get 'serious'
What do I miss? - Nothing! ... honestly. I loved the D800, but I always felt it had to have the best of the best lenses attaches to get the absoloute most from that beastly sensor. It was also awkward and cumbersome to just casually take out. It had become a thorn. I would only take it to very specific outings. I certainly do not miss having 6-7Kg on my back for just heading out for a walk or cycle!!
It's just gear. Once you have a capable set up that you can relate to, stop worrying about makes and models and even sensor sizes. I had gotten lazy with full frame tbh. I'd take shots and think 'I can crop the hell out of that later' - I am much more aware now of NOT doing this. And still finding my images are plenty good enough IQ-wise
Selling the FX gear helped me pay a lot of bills also, even after buying the Fuji start up.