The problem is that if she knows what the reward is, she may anchor on already having the reward, turning it back into negative reinforcement - if you promise your kid a trip to Disneyland if they get above a 3.5, and they get a 3.3, they feel like they actually lost something. The use of a gambling mechanism may be key for this. If your reward is a chance at a real reward, you don't anchor as already having the reward, but the reward still excites you.

So the technique described here requires thinking that an X chance of Y is better or worse than a certainty of XY?

We could do with some alternative approaches to ugh field defeat, so here's one.

Yesterday, when I was trying to decide to go to bed (just "to", not "whether to"), I managed to create an effective "counter" ugh field to staying up, by considering that at the same time I'd be worrying about the results, failing at something so very basic, and turning back to the hellish failure mode of losing self control in general (A phase I consider my worst experience of all (admittedly short) time).

I don't know whether the last point is something everyone goes through at some time (like a second puberty) but I'm sure you can come up with your own points to mount counter-ugh-fields on.