This question is all on the title.
English is written in the way that each word is separate.
Then how about pronunciation?
Does a break appear, separating words while you pronounce?
Or is it not necessary in physical world as real sounds, but it is always true in your mind?
Because, I’m native in Japanese and usually, and don’t care about separation of words both in speaking and writing, this question comes to me. And many people in Japan seem true of the case, not caring about the separation.
Please think about it.
The short answer is “not usually.”
Text segmentation–for example, the boundaries between words in print–is a different phenomenon from speech segmentation. Anyone listening to someone speaking a foreign language will be hard-pressed to determine where one word ends and the next begins. Semantic context, grammar, and other contexts are required to know where one word ends and the next begins.
Boundaries in print are a different issue. Different languages use different kinds of orthography, and handle segmental boundaries differently.
In different language there are different contexts where people pause, (e.g. in English people do often pause between clauses or phrases, and between sentences). But generally, airflow continues without discrete pauses between words. There are even ways that adjacent words change each other’s pronunciation slightly (e.g. saying the n sound in “in case” more like an -ng sound).