Oh well thats simple . aha for one writing doesn't require face -to-face talking so any nervous habits or awkward silent moments can be eliminated . Learning a new language is fun and writing is definitely a huge step in learning but if you can't say what you wrote that could be a problem . My parents are both spanish but i never learned spanish until the end of last year so I'm rough in speaking it even though I definitely write it well enough. I always get nervous or worried that I'm pronouncing a word wrong or I blank out on what to say since in writing I can at least pause and think about making the sentence perfectly sound right. Its hard but honestly practicing with other people even if you make mistakes is super helpful because they can help you correct your pronounciation and after a while it'll be normal because repeating words over and over again ..haha its gonna eventually become part of your basic vocabulary.