Most Helpful Girl
Surround yourself with people who care about you and make you feel good and happy.
Keep yourself busy, either with those people, or start a new project (like redecorating, learning something new, etc). Maybe start a new routine, visit some new places that could be fun or good for you.
Watch good movies that make you feel good, probably stay away from romantic ones that'll just make you think of him.
Make new friends at work, if you can, develop friendships.
Good luck and I hope you start feeling better soon!