Marketing theories driving me MAD!

I just realized, after finishing my master degree 10 years ago, I have lost my 'theoretical senses'. To begin with, I never had much talent in this area. I am a pragmatist, an inventor, a creativist... even during my days as a young student. However, when I was young, despite much challenge, I could still absorb something although with much efforts. Today, at the age of 42... I tried very hard to read and understand marketing theories, and proven almost IMPOSSIBLE! Somehow, nothing make any senses! Oh my, must take a break and start again!