Relax. Don't try to be overly formal. Use an informal, conversational tone. Make the reader feel comfortable and understand you easily by writing like a peer, not a robot.
Have you ever had to deal with customer care agents? Most times they deliver their canned lines of "We sincerely apologise for the inconvenience. Please bear with us." It sounds so generic. My best experiences have been with those that reacted like humans. "Oh no, that shouldn't have happened. I'm sorry about that." Regardless of their sincerity, using common language like that broke down barriers, and felt like they were actually listening.
Adding personality doesn't mean loading your writing with slangs, memes and jokes. It means being honest with your audience and writing in your regular voice (with good spelling/grammar, of course), not some robotic voice.
Also: we're in 2020. It's okay to use emojis to "flavour" your writing. But use them sparingly, so they aren't distracting. Don't rely on them to convey meaning, just like you shouldn't rely on the colour of a button to say what the button does.