²⁰One aspect of uncertainty which is not explicit in the frustration equation is the RPE due to changing predictions. Suppose one moment you think you will get a reward, but the next moment it looks like you will not get it. This decrease in expectation induces RPE and thus suffering (as explained in footnote 20 in Chapter 5). However, nothing may have actually happened, it was all just predictions in your mind. Importantly, such a change in prediction is only possible if there is uncertainty. If the future were certain, there would be no need to update your predictions, but because of uncertainty, the predictions change from one moment to another. Again, such suffering can be reduced if you realize that your predictions are uncertain; then the change in the predictions would be given less weight, as just explained in the text.