How can I get over having feelings for a coworker?

I am finding it difficult seeing him everyday and feeling embarrassed as I’m an adult and everyday it’s getting worse and I leave work feeling deflated everyday.
He recently got back with his ex and I respect that so want to distance myself.
We have been extremely flirty with each other in the past and he is always so nice to me but I know nothing can happen.
He is also slightly older than me (15 years older) so I don’t think he even thought of me that way..

I don’t want to be mean to him but how can I get over my feelings for him.

So far I’ve tried some things to distance myself, I don’t approach him anymore unless it’s work related and I keep conversations short, I stopped liking his photos on Facebook/Instagram, he has stopped liking mine and he has stopped texting me.
Which hurts and makes me think maybe he did like me if he feels he can’t even text me anymore.
I also can’t move department or change job either.
How can I get over having feelings for a coworker?
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