Hello Darren,
I know exactly what you mean. You start working in the studio full energy and inspiration, and nothing works the way you want. At the end of the day you have nothing at all, and it feels like a waste of time.
Sometimes I try to argue that it's ok what have made after such a day, but eventually ended up in the trash anyway.
It happened to me with some Jam's, who never appeared on youtube :-).
I have no manual how to deal with that, but what I usually do is this:
Once I notice that this is a wrong day, I go the opposite direction. Try to let go of what you are doing and create something totally different than you had planned (because continue what you are doing does not make any sense at last). For me it helps to do something totally different, instead of a little different. (and perhaps other gear if you have that option).
Another thing I try sometimes is to change my workflow, by changing the order in which you are normally create tracks. That gives me a new perspective on an idea, and helps me to go forward.
If that doesn't work, I stop creating and go listen to music for a while. Sometimes that will reset my inspiration, so I can start all over again with a new idea.
I have accepted that this happens once in a while, and it gives me confidence to know that I'm not the only one