How are you organizing and using the knowledge you have acquired?  There is foreshadowing in life.  It's uncanny how a skill you pick up in a seemingly unrelated field of study can be applied to something you encounter in life, often years later, that makes you think, "Man, I sure am glad I learned _________." Don't underestimate the usefulness of what you know and have the opportunity learn.  Don't sell short the fact that what you think is not important may become vital to your future success.

Furthermore, it's important to be applying the things you already know to your every day life.  Think critically.  Be like MacGyver.  You will lead yourself into a mediocore (or worse) existence if you walk around like a zombie mindlessly following a crowd and gnawing on the people truly living.  The more you apply your knowledge the easier it will become to apply.  

It's great to learn as much as possible, but chances are that you'll never win a million dollars on Jeopardy.  Knowledge is only powerful when applied.  For example, I started programming computers when I was in high school.  Later it came in handy when I performed computational chemistry research in graduate school - where I learned even more.  Now, I am applying that knowledge to programming this website and neural network research - which was never my plan for life.   

Take the opportunity today to consider how something you already know applies to something you are either currently learning or doing.  If done often, this will train your brain to recognize opportunities that you may otherwise miss.  You will become like MacGyver.  Don't be the person that says, "I wished I would have paid attention when ________."  Be the person that says, "Man, I sure am glad I learned ________."