dont ever think like that...did you enjoy yourself in those 4 years? you only live once and theres no point and sitting around complaning about how you "wasted" it because if you really think about it..your wasting more time complaning about how you wasted your life...so get up go hang out with some friends and smoke a joint and forget about how your wasting your life.
and if it was a girl you were seeing for 4 years and you recently broke up with her i learned something very important about this..its better to love for 4 years then to not love at all no matter how much it hurts when it ends. trust me

peace