Nothing except rocket science, is rocket science. UX writing is a skill anyone can learn. With a few books, a couple more articles and some common sense, anyone can write UX copy that doesn't suck.
Here is a collection of all the resources that helped me become a better UX writer:
Why UX writing is important
By Edwin Mohammad
By Akhfhin Rahardhiyanto, Nadila Dara, & Nadiya Amalina Saptari
Why your design team should hire a UX writer
By John Saito
By Jennie Tan
UX writing fundamentals
By Apple
By Kinneret Yifrah
By Torrey Podmajerskey
Working with designers
Voice and tone
How to write digital products with personality
By Nick DiLallo
Can a bank sound friendly and professional?
By Naomi Goh
Tone of Voice: Reviewing good examples and best practices
By Ben Davies-Romano
How the persona of a product shapes the voice choice
Phoebe Ohayon
Duolingo's voice and tone guidelines
Content testing
How to test content with users
By Kate Moran
Content testing and measurement
By UserTesting
When should we turn to content testing?
By OneDesign
How to test content like a pro: A step-by-step guide
By Ryan Williams