Musings of a peripatetic wannabe-sage: Going with the flow or striving against the tide?

I'm not very far into my dissertation, but I can already see the effects of tiredness and stress on output. There are days when I just can't work. I try to do a little something even then, just to keep forming habits. I keep reminding myself that it's a long process, that I work full time, and that I have time. But there is a fear that the tired days will begin to be more common than the motivated days. Still, some days I do think it's best to set the books aside and play a game on my Android.