The only way to solidify grammatical knowledge, verb conjugations, even to automatize formulaic greetings, ultimately any form of expression in a foreign language, is to practice. It especially helps if you communicate about real issues that you are invested in and even better if it's with native speakers who can give you good input in return. I remember the first few times we had discussions in French class that I actually cared about; we were just getting to the level of ability where we were able to express coherent thoughts and opinions and when the topics that came up were ones I felt strongly about and even disagreed with some of my classmates on, it was such good motivation to try to communicate clearly. The desire to express my thoughts on those issues helped make the expression happen, and even though it was imperfect the process helped to improve my abilities.
An important aspect of practicing language and improving is letting go of the fear of embarrassment; it has been shown that language learners who are more gregarious learn faster and are able to communicate better than us quiet ones, even if they make more mistakes in the beginning. (I should put some studies here to back it up but I just remember reading about it in lots of different places.) Knowing this, I worked on this skill in a way that resulted in an interesting language experience for me. I pushed my boundary of "waiting until I have it right" and made a fool of myself, but in the best way. What happened was that during an interview with Kichwa speakers a kitten walked into the room and as we were petting it and playing with it, I wanted to express the idea "what an adorable/delightful kitten." So I said mishki misi, "sweet cat." Unfortunately the word I chose for "sweet" only carries the meaning when associated with food and doesn't extend to people the way I would use it in English or in Arabic. I realized right after I said it that this metaphorical connection probably wasn't the same in Kichwa, and this was confirmed when the whole room burst out laughing at my mistake and repeating it. "What a delicious kitten," I had basically said. Even the word delicious extends metaphorically to the cuteness of babies sometimes in English, so it would almost be more accurate to say that it sounded like I had literally been contemplating eating the kitten. That's the image that my sentence created, anyway.
The point is that as embarrassing as that mistake was, it was possibly the best thing I could have done. It was funny, and making an inadvertent joke like that brought me closer to the Runa people I was with. It lightened the atmosphere and changed some of the awkwardness of trying to do a formal interview (probably something to do with the power dynamics as well, making it clear that I was a learner and not just a know-it-all scholar/native speaker of English). I realized that I didn't even have to let everyone know that I understood what I had just done wrong because being able to laugh at myself about it showed a conviviality that they appreciated.
So unless I let go of my fear of making mistakes in speaking other languages, I will never be as adept as I hope to be and that will hold me back from communicating with people in meaningful ways, which is a much higher goal than being right all of the time. In the same way, my writing will only become worthwhile in the way that I want it to be if I put in the hours of practice and revision and more practice to make it better. This conflicts with my instinct to write a few words and strive for conciseness. Just being careful about what I write when I do write is not enough: spending time thinking and writing and putting my thoughts into words will help me develop them so that my ideas will actually become better. Using concrete words to express my ideas will not only force me to improve my analysis, it will make it possible for others to understand my ideas and react and contribute in return. Letting others read my writing has the additional advantage that some may be able to help me to form these thoughts even more clearly.
To return to my self-doubt from earlier, the answer is that I can't create anything worth contributing without this practice. And it's probable that I will never come up with anything truly compelling and worthwhile until I write lots of junk, and I don't need to be too embarrassed at my poor writing skills (and posting them online, publicly!) because I can see them as evidence of improvement instead of evidence of my incompetence. So instead of feeling weighed down by the task of writing and the visible trail of my shortcomings, I'm going to be excited about how all of this writing experience is preparing me to live up to my future aspirations (published papers, more academic work, yada yada). Right now in the present, and not despite but precisely because they are imperfect, just like my decision to say mishki misi.