What brings change in life?

How can I change my life? When i look back and see, I feel that there were times when I had been constantly 'developing' but now I don't know why that zeal is lost somewhere. I used to be so ambitious and aggressive for my dreams but since last one year, all my energies have literally gone down. I don't feel like doing anything. I don't have any job. People at my age are so career conscious and they want to achieve so many things in life, even I used to be like that. I was once the most "discussed topic" among my teachers & friends (of course in positive way). But gradually, I don't know what happened. Everything changed (inside me). And believe me, I am hating all this. I'm so directionless. Please advice how can I bring myself back on track.

Thanks.