Yes, I wrote the petition letter (16 pages) myself.

I spent lots of time working on the cover letter and the recommendation letters. I have to do experiments in the day time and worked on my GC during night time. For about 2 months, I used to work until 1am and got up at 7am.

Got some help from several friends in my university, and got some free sample letters from this forum but unfortunately not helpful because of different field.