Question: I don't know how to put it. I have never published before. Previously my one paper was rejected, that was because the experiments were not ready and my advisor asked me to still submit it just to have practice.

Now, 6 months later, I am writing another paper (on a similar topic). I have done some experiments, some are still going on. My advisor had advised me that "even if your experiments are not complete you should still start writing the paper". 

But I'm doing a lot of procrastination and I think I am scared of writing and possible rejection. I have done a lot of writing in other forms before, like blogging etc. But the thought of writing an academic paper with all the stringent rules (everything has to be clearly written, cited, nice flow of thoughts) is scary.

Please let me know how should one's mindset be while in the process of writing a paper.

Answer: 
If you didn't have any **scientific writing** class before, I think you should start buying a **book** about it, and read it.
There are many titles avilable.

If you get one, it can give you some **good advice** on how to write (good) scientific papers.
Rejection can be hard to handle, but a good motivator is to look at people who's work was rejected initially widely, but ended up being immensely popular and profitable. Ghostbusters was rejected by three movie studios. Frank Herbert's manuscript for Dune was rejected by over 20 publishers. Lorenz's seminal paper on chaos was rejected several times if I remember correctly.