Most Helpful Guy
Set yourself a new goal to achieve and go smash it
Most Helpful Girl
"He was my everything" <---THIS is why you're feeling unmotivated... you lost yourself in the relationship.
In order to feel better, you have to focus on yourself first. Set goals for the next few months (fitness goals, beauty, career, etc). Focus on making yourself a "new"/ best version of you. Watch a Victoria's Secret fashion show, and see how those girls ooze confidence and are totally full of themselves. Sounds shallow and superficial - but you have to be a little full of yourself to be more independent emotionally.
Second, get the book "Art of Seduction" by Robert Greene. It helps level set your emotions and outlook on love and relationships. And prepares you for your next relationship
Third, even if your heart isn't in it, and you're not emotionally in the mood, STILL put yourself in a position to meet someone new. Whether online or one of those Meetup groups. And don't limit yourself to just one person... Personally I like Tinder lol (just avoid the guys who are obviously only after sex). Meeting someone new and feeling a little spark of excitement when you click with someone is part of the healing process.