sounds to me like you are being too intense with your trials. making it too stressful. If you hit a block of failure. Have a night or two off, get your recall up, and revise your method (ie work out exactly what you are going to do next time you try)

This will get confidence up (important!) and youll go back to be less tired and more succesful hopefully...

If I fail a WBTB (often...lol) then yeah I feel tired
If I succeed, my day is spent in a euphoric mood! so, im only tired when I fail...

but definately take a break from WBTBing for a night or two

goodluck