When lacking inspiration I normally take an old 3D scene and play around with it.
Or have a look at other people work and focus on one that catches me,
First replicate as much as possible then try to make it better and make it my own.
Changing point of view can do so much sometimes for a scene.
Making a series of something is to keep busy with your craft/skill/art
Just find a way to get inspired
Not reaching your goals? Not everything is easy to master.
Mastery takes a lot of time..
Things I heard some of my mentors say about skills.
"First 1,000 Hours is the time of apprenticeship, but it takes 10,000 hours to master."
Inspiration sometimes comes at the most awkward times. be sure to record it ASAP.
Sketch/ make a note/ etc, so when the moment comes you have time you can recall it.