There's a simple, but strange, solution: a Big Red Button.
In an experiment, subjects were given complex tasks to complete while loud noises emanated from the next room.
They were told it was important work going on, but that if the noise got to be too much for them, they could press a big red button and it would stop for 10 minutes. They were, however, asked not to press it if possible.
The control group, ironically, was not given control over the noise.
Not surprisingly, the group with control over the noise by means of the big red button did better on the task than the control group with no control.
What is surprising is that none of them used it.
Further, even when the button was disconnected and would have no effect (unbeknownst to the subjects) the effect was the same, proving that it was not control, but the belief of control, which reduced the negative effects.
When I'm facing a daunting challenge, one I've imposed on myself (posting daily on Instagram, riding my bike every morning, skipping dessert) I sometimes mentally give myself a Big Red Button: if the effort gets to be too much, I will allow myself to push the button and tag out. Skip posting. Skip the bike ride. Don't skip dessert.
I rarely press the button. I do, once in a while, sometimes just to remind myself the my button isn't disconnected; I can use it any old time I want.
Giving ourselves permission to bail on a difficult task (one with no costly downside) is often the difference between burnout and motivation.
You need a Big Red Button. Push it. Don't push it.
But keep it handy. You need it.