How will you keep it? By listening to this knowledge and refreshing yourself with this knowledge. Everyday listen to a talk about knowledge or read a book on knowledge for a few minutes.
When you are driving, turn on some knowledge CDs.
When you are struck in a traffic jam, instead of thinking rubbish or singing some useless songs, delve into knowledge.
I am not saying you should not sing songs. Music is important but along with music spend a little time dwelling on knowledge as well. That will help and your sadhana will help.