Yes - every single day (unless you have specifically scheduled a day off - that is a good idea too!). Not everything you write has to be, or will be, perfect. Don't worry about that. However, you do need to write this regularly in order for your work to get as close as it can be to being the best work you can produce. Train yourself. You wouldn't turn up to run a marathon without training, and nor do you expect that you can run your best time the first time you try. In the same way, you need to train your mind to concentrate and write extended pieces of work.

In Writing Your Journal Article in Twelve Weeks, Laura Wendy Belcher suggests writing for fifteen minutes per day. You might also try aiming for a word count - around 500 words per day is usually a good balance between making progress and not exhausting yourself (because you need to be able to do it again the next day!). 500 words per day is 182 500 words per year! Imagine how productive and prolific you can be if you're sticking to this!