How do i get over such heartache in my life?

im struggling at the moment, i have lost my girlfriend of 7 years, the girl i was ready to spend the rest of my life with and my job, and now i spend all my time at home depressed and uninspired, i feel so low and i keep going over my mistakes in the relationship and being completly unforgiving to myself...most of my friends are in relationships so i rarely get chances to do something else, are there any suggestions of things for me to do to get over the lowest point in my life ???