That's the whole point.

Relationships, for the most part, are just trial runs. They are just individual experiences that you share with another human. Everything ends eventually.

I think if you accept that, and try looking for a healthy relationship with someone, rather than a never ending one; you might loose the existential dread of a 'failed relationship'.

As well, practice makes perfect; It might be difficult but the best way to advance your communication skills, with people, is practice. That's that. There are tricks you can learn to help, but just get out and meet people.

Aiming to do something social everyday, that makes you uncomfortable, is a good way to start practicing.

Good luck. Stay hard.