To not be stuck means to be able to change gears mentally. Put it in neutral for a bit and take a break, relax, rest. Or coffee.

Either push through the roadblock with everything you have like it's due the next day and ride that momentum or hold back and find inspiration in little things: the sounds around you, the sights, the local wildlife (coworkers ;).

And don't forget someone else has probably had that EXACT problem and solved it so you may just luck out if you can google the right search.