The usual rule of thumb is that you spend 50% of your time on the hardest 5% of your flashcards. [...] There will be cards that behave this way; that’s just life. Do keep an eye out for them; try and learn to recognise the mental state that is “urrgh, not this card again”.

1. Ditch the card
2. Split up the card
3. Make better mnemonics or change them