One of the most common pieces of writing advice is to "just get words down on the page; don't worry about detail, and don't think too much". This is often given as a way of overcoming writers block, or the "fear of the blank page".
Perfectionism is seen as a bad thing, because it can lead to constant and never-ending revision of every sentence.But in academic writing, accuracy of expression matters, and there are some things you need to get right.
If you write a sentence starting, "the purpose of this study is..." then it is absolutely essential to express yourself accurately, because the examiner will judge everything that follows based on their understanding of that one sentence.
Be patient. It is worth spending some time to perfect it.
Your pace should vary naturally with the difficulty of the concepts you are writing about. Obviously, difficult ideas take more time and work to express in writing than easier ones. So if you only write fast, you can only cover easy concepts. If you have to slow down to think and find the right words, that's OK.
Be patient. It's worth spending time to clarify the idea.
Deal with problems as they arise
I think of writing as a problem-solving process; finding solutions to problems of expression.There are always difficult problems to solve, which break up the flow of the writing, but it is is important to try to solve these as they arise.If you put yourself under pressure to keep producing and jump to writing about something else, then all you are doing is saving all the difficult stuff for later (when you might be under immense time-pressure).
So try to stay with the problem a little longer. Be patient. It's worth spending time to find a solution.
The sweet spot
Total perfectionism, where nothing is ever good enough, is clearly a bad thing. But total carelessness is a bad thing too.The ideal approach lies somewhere between the extremes, where it's OK to take care over your writing. It's OK to slow down and think. And sometimes it really is OK, even necessary, to be a little bit perfectionist.