My memory goes to sh*te in two different cricumstances
1. I'm tired
2. I've got to much on my plate workwise. Which then leads to cr*ppy nights sleep see point 1 above.
I find in extreme circumstances I loose my motivation completely and the only thing I want to do is slob on the sofa and state blankly at the TV for hours and not move.
I know when I feel like that its got to bad and I need to do something about it. Which is namely
1. Clean my desk at work, clean all the crap off of it and have a clean desk.
2. I then write down a list of jobs that I need to do on my pad and then when somebody tries to give me something new to do. I write that down on my list and say, well your task isnt getting done until all these others are. The only time I'll change this is if the problem is order flow effecting as thats where our core priority is.
I find if I can fix the things at work that make me feel like this I'm more motivated to do stuff when I am at home and I am less likely to slob in front of the TV.
I think I suffer like you Grinch I get mentally drained and then I have no capcity for doing anythign else. I find the cycling I do helps as I dont think about things when I'm cycling I just pedal and everything kind of washes over me. If I've had a bad day by the time I get home I feel alot better.
Its difficult to deal with and even getting up off the sofa can be hard some days. Especially when all I feel like I want to do is to shut the world outside and withdraw into myself.
