As someone who naturally loves to write, it's somewhat hard to explain the fundamentals and put it into perspective for what helps me, but ill try giving you some of my ideas that are the steps to improving, and I might expand upon this in the future.
1. Writing, you have to have atleast some passion for it. If you go about to do something that you don't want to do, aren't you tempted to just quit? Get into a hang of writing on your own good will. I tend to write fun little short stories when I'm on burn out and do often read things that spark me to get into a mood (similar to what cloud said!)
2. Know the material that you are writing about. Want to make actions about let's say a medical procedure? Well, you don't have to necessarily research and sell your soul to the topic, but you should atleast look into it slightly.
3. Don't just put length into what you're saying. Detailrp isn't all about the amount of words you use, its about how you utilize those words to make a sort of scene for your character. Repetition isn't always fun to read, atleast not in one sentence.
4. Get into the right head space, a vibe! The BEST thing that helps me write is listening to music, like right now! I tend to make different playlists for my characters so I can kind of shift into their personalities and go with the writing flow.
5. Word play and environmental use. This is pretty self-explanatory but the better you are at wording things and involving the people near you, the more likely you are going to have some j u i c y actions.
What about confidence? First off, I'll say the straight forward answer; it depends on you, and how you act as a person. If you are someone more introverted, you're less likely to go up and converse with someone in the community unless you have good socializing skills online. Along with this, your writing style factors into it ALOT. Some of the best ways to give your character confidence is by using bold words and emphasis. If you make a bigger leap in your word choice than it'll help a ton, of course this plays into how you write overall. Some ways people add emphasis to their actions are by utilizing the color codes (aka &o &l and all the other ones).
Here are some writing examples:
Character Action A: She walked up to the man. [Insert character name] looked angry, stomping her foot into the ground! "HOW DARE YOU!" she screamed at him.
vs
Character Action B: The girl trudged towards the mid-aged man with a cold glare, looking furious. [Insert character name] slamed her boot into the ground, causing a deafening echo to pierce through the empty hall "HOW COULD YOU!" she shrieked out.
Character Action A: [Insert character name] looked to the side, as he felt someone watching him. . . Listening to the sounds near him more closely now. He made a hand gesture, telling his friend to be quiet. . .
vs
Character Action B: [Insert character name] spontaneously turned tense, the color draining out of his already pale face. . . The hairs on the back of his neck stood up in response to the rustle coming from the side. Quiet as a mouse, he motioned towards his friend that something was off. . .
Questions, concerns, NEED A FRIEND(?!), or anything else you want to know; drop me a dm Sonder Occhiolism#5865 would gladly help, and this goes to anyone reading this - I will try my best to respond, yet it might not be right away.