The fundamental truths of Taoism:

Things change.

People change.

Situations change.

Nothing ever remains the same.

What is most important is to adapt to these changes as completely as possible.

You are now a single person, so you have to restructure your life so that being single is enjoyable, rewarding, and fulfilling.

Look at all the possibilities that are now open to you because you are single.

Don't sit and look into the hole where your girlfriend/boyfriend used to be.

Live your life.