How do I move on after my narcissist partner discarded me for the second time?

We were together for 3 years. He was my first real boyfriend. We had a stupid argument 2 weeks ago, which he started and he hasn’t contacted me since. I didn’t expect it at all, there were no hints, signs, whatsoever.
How do I move on after my narcissist partner discarded me for the second time?
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