Half the battle is turning up. Half the battle is coming back to your work after taking a break, several times if necessary. And half the battle is getting in the right head space (all battles command more than 100% from you). This can be helped by travel, sleeping at a different time from usual, being ill, drinking, drugs...so plenty of danger there for mistaking one thing for another. The best way to get in the right head space for taking photographs is 1) start taking pictures straightaway, bad ones especially (or very vaguely interesting ones if you prefer) 2) get closer 3) keep moving 4) get above people and look down 5) get below and look up 6)take more bad pictures 7) get closer . As William Burroughs said, good writing happens when your nose is right on the wheel in front. Writing and taking pictures are similar in that when you are in the right headspace you see possibilities everywhere.
Of course one of the main enemies of the right head space is getting precious about being in the right head space. You need to get rid of any pressure- self imposed or other-people-imposed. You need to be outside time- achieve this by other going very fast or very slow, machine gunning or simply staring. Increasingly, though, I find that almost any photos are good, almost any writing is good. Maybe the right head space is simply the one that says 'make something' rather than "it's not good enough". Not good enough for who?