How do I move on from her?

Over the last few months I've had a crush on a girl from work but at the time she was in a relationship until a few months ago when they broke up... I recently gained enough confidence to ask her out but she ignored the message which obviously I know now she's not interested..

I can't stop thinking about her, Like everything I do I see something that reminds me of her... For example a few days ago I driving about and saw a street name that reminded me of her, Going through Instagram she pops up on the explore page thing...

And saying "Find another girl"... Isn't as easy as people say it is
How do I move on from her?
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