There are different kinds of progress that you can make as you write.
You can produce text that makes it into a specific draft. You obviously need to do this eventually, and perhaps you even do it from the start. But, I think, it's not the only kind of progress you want to be aware of.
You can develop the prose style that you will use for the piece you're writing, your "voice", the atmosphere and tone and attitude of the piece. Perhaps you throw away some specific block of prose, but if, in writing that prose, you moved towards figuring out a compelling style in which to tell your story, then you have made valuable progress, and the next prose you write will be better.
You can improvise or improve the structure of the story. Of course, you may or may not have already worked on an outline. In any case, by starting to actually write prose you will develop your understanding of the story's structure. Even if you throw away any amount of prose, this improved understanding will help you do better in the next attempt--and, of course, it is by no means necessary that you do throw everything away.
You can discover who your characters are and where they are going by writing about them. Keep or reject the actual prose--as above.
As you make progress in each of these areas, you will get a better idea of what you want to do in the others. This may mean re-writing or editing prose that previously seemed good, or figuring out how to write decent prose when previously all you felt you could produce was, as you put it, "bad words".
It is quite reasonable that, if you do not have good characters, an effective narrative structure, a compelling voice for this story, anything you start writing is likely to sound like "bad words". If the process of writing "bad words" helps you make progress in any of these areas, you will be in a much better position to write something good afterwards.
Nevertheless, I do also recommend that you consider outlining or otherwise planning before you start writing. Different people prefer different strategies and this is a very large discussion, but it's worth pointing out that you at least have a variety of options that are worth trying so as to see what works for you.
An altogether different issue that you might face is that, perhaps, you are doing exactly the storytelling you want to be doing--you're putting the desired characters, plot, etc. on the page just as you want to--but the quality of the prose itself is bad. In this case, it makes good sense to get the entire story written down, so that you have a complete draft to work with. Then, you can edit to your heart's content, until the prose itself is well-done.
EDIT: By the way, all this is relevant to some other common writing advice that I think needs some extra context: "don't re-write". Yes, if you keep re-writing your first chapter forever, you will never complete a story. Yes, if you keep re-writing a block of text in order to improve it in a single area, e.g. trying to get the perfect hook and atmosphere in your first chapter, you will make slow progress in other areas of your story, or none at all. But I think it's OK to re-write after making progress of the kind I've described above. If you have developed a better understanding of your story overall--its characters, structure, plot, etc.--and you now see that some already-written prose does not fit your new understanding, well, then, fine, re-write that material if you want to...