The slump will always set in at some point or another. One method I've always found helpful is finding something that makes you excited to do something. Sorry to use a motivational quote here, but there's a lot of truth in this:
"Action isn't just the effect of motivation; it's also the cause of it"
A lot of it is just starting with something and push through. And if you have a bad week, then so be it! Unlike what people tend to tell themselves, you don't always have to improve on previous works. You'll have bad days/weeks/months. It's par for the course. Don't sweat it, just make sure to put something out smile