Before Epic, I used to dev for a couple of Indie studios and what I always found helpful was when I had the feeling of banging my head against a wall, complete artist block, or just being tired of devving, I would go do something completely different. Go outside for a walk, visit a museum or gallery, spend time with my family - just something away from a screen.
During those times I would be subconsciously stewing on everything, and would often have those ‘eureka’ moments of how to fix the issue, or be inspired for a mechanic or visuals while doing something completely different. That inspiration would re-spark the creativeness and I’d start being super productive again! (Also good music helps, I’m a massive fan of listening to orchestral pieces from games or films while I work).