Depression, Unable To Concentrate, Affecting Career After Getting Rejected By A Girl. Solution?

Hi. my self sanjeev , age 31 years. height 160 cms. 5 years back i proposed a girl but she rejected. then after i tried to contact her may times.I followed her in public place. and simultaneously i was busy in my job. MY problem stated when she took the admission in collage just near by my office. I saw her many times thats region i started sending text. Till now i never forget any one single day. last 4 years i thought each and every single days. morning, evening, night. At my office,friends party,while travelling. I left the job because her, i was regional manger of one of the leading finance company. please help me. sanjeev 0000