بسم الله الرحمن الرحيم

1. To abandon asking
2. Not silently listening and not giving an attentive ear
3. Misunderstanding or wrong understanding
4. Lack of memorisation
5. Not disseminating and teaching it; for whoever accumulates [and keeps knowledge as a secret] and does not disseminate it, Allaah will afflict him by making him forget it- as a just recompense.
6. Not acting upon it, for indeed acting upon [knowledge] compels one to remember and ponder upon it, guard and examine it. But if he does not act upon it, he will forget it.

[Source: (غذاء الألباب) – page 33’ By Muhammad Bin Ahmad Bin Saalim As-Safaareeniy Al-Hanbali (rahimahullaah). Abridged & slightly paraphrased]