With regards to the student of knowledge working hard to acquire al muroo-ah (fine and honourable manners), Shaykh Muhammad ibn Saalih al ‘Uthaymeen rahimahullaah comments:
So if a person were to try to gain those (correct manners), and his inherent nature were not (naturally) like that, then he would encounter difficulty.
However with practice, he can improve his condition.
And this is something shown by experience. For we have heard of a person who was far removed from al ‘ilm (knowledge) and from seeking knowledge, having evil manners.
Then when Allaah bestowed upon him the blessing of knowledge and guidance, his manners became good because he trained himself upon these manners until they became just as if they were from his inherent nature and his natural disposition.
(Sharh hilyah taalib il ‘ilm p40 of Shaykh Muhammad ibn Saalih al ‘Uthaymeen rahimahullaah, translated by Nasser ibn Najam)