Ask yourself whether you've just got the shite british weather blues?
The weather is starting to improve, get out on a group ride or set yourself a day where you have no other plans but to ride your bike, get the headphones in and ride by yourself, no camera, no pressure, until you can't grip the bars. The former is more fun, but the latter certainly helps as well.
If its not just weather blues, then here are my thoughts;
May try mixing it up, sell the bike you have and get something different. I first switched to a hex, then to brakeless, then on to 24" bikes.
Mix it up. Get out on the rocks, ride street, go to new places. I don't ride my trially as much as I used to, nor do I feel I am as good as I used to be, however I enjoy riding more than I ever have, and as such I will ride anything I can get too
having an off day? Don't ride - If you force it, you'll hate that you can't manage something you were doing yesterday, that causes an increase in stress, and thus negative connotations towards riding (#firstworldproblems).