Muhammad ibn Sallam, the haafidh from the past, as mentioned by al Dhahabi (rh), that he was always eager to write down in class. One day his pen broke and he said in class, who will give me a pen for a gold coin!
It shows how important it is to make notes. He was a haafidh, which means that he had memorised 100,000 Hadith, and yet he’s still making notes!
You might remember something today but won’t remember it tomorrow and definitely not after an extended period of time.
You can’t act upon something unless you have it documented correctly!