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: 
One thing that might help with the fear of rejection is to view your paper as though it was a blog post. Obviously, you won't submit something in blog style to an academic journal, but it might help to think about why you blog. You have ideas and thoughts you think are important and you want to share them with a wide audience, who might be interested in your ideas or use them as a jumping-off point for something they want to do. The purpose of an academic paper is the same (well, in addition to the career benefits of publishing). You want to share what you're doing with people who will be interested in the results, and who might find inspiration for their own work in what you've done.

It might even help, as an exercise to get past writer's block, to write a blog post about your research. (You may not want or be able to actually publish it on your blog, but it might help your thought process either way.) What are you investigating, what are your methods, how is it going so far, etc.? You can then take some of that material, formalize the language, add the appropriate citations, and include it in the appropriate sections of your paper. But picturing your blog audience, rather than some journal committee, reading your first draft might take some of the pressure off.

Another thing I find helps me with fear of failure is to accept that the first draft of anything I write will be crappy and focus on getting ideas down and revising later. I also found, at least as an undergrad English major, that it's easier to just write late at night. Something about being tired takes the edge off my self-criticism and gets the ideas flowing. I describe it as my internal editor going to sleep by ten o'clock.
Like anything else in life, perform the task with the goal to succeed, and the likely outcome of failure.

Understand that rejection is all a part of the game. Very few people succeed more than they fail. As a matter of fact, upwards of 90% of all academic papers are rejected for one thing or another.

The most important thing is to keep track of mistakes that you've made with past academic papers. Write them down as bullet-points on a separate sheet of paper. Keep that paper right in front of you as you work on other academic papers to remind you of what **NOT** to do.

Practice makes perfect. If you're just starting out, it's likely that you're going to have many failures before you have a successful one.