On how to avoid diet fatigue see Israetel 2019, p. 23.
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Adopting a 'done is better than perfect' mindset means to accept that every once in a while, things can get a little out of whack. These are crucial moments when it's important not to abandon everything with a *perdu pour perdu* mindset.
Sometimes, indulging in just a little bit of vice once in a while intentionally can get you fully recharged in terms of willpower (for instance for your diet).
I think the keyword here is **INTENTIONALLY** as planning and choosing to eat a burger once a week can be lots of fun, but succumbing to a craving is more likely to lead to guilt.