This ability to make judgements about our own minds is called metacognition. Studying it has identified other misconceptions too. For instance, many of us think that actively thinking about trying to learn something will help us remember it. Studies suggest this is not the case. Far more important is reorganising the information so that it has a structure more likely to be retained in your memory. In other words, rewrite the content of what you want to learn in a way that makes most sense to you.
Knowing about common metacognitive errors means you can help yourself by assuming that you will make them. You can then try and counteract them. So, the advice to space out our study only makes sense if we assume that people aren't already spacing out their study sessions enough (a safe assumption, given the research findings). We need to be reminded of the benefits of spaced learning because it runs counter to our instinct to relying on a comforting feeling of familiarity when deciding how to study
Put simply, we can sometimes have a surprising amount to gain from going against our normally reliable metacognitive instinct. How much should you space out your practice? Answer: a little bit more than you really want to.