Ecophys

Write. It doesn't matter what it says for now. Don't worry about the flow, structure, etc. Just write. Get your thoughts down on paper and rearrange them into a thesis later. If you are writing a MS based thesis or writing in definable sections, write the sections that come easiest first and then address the more difficult sections at a later time. When you get to a section that has been giving you trouble, have a couple of drinks and try again. It might help.
 
Exercise is a great way to break the block. In general, anything that can take you mind away from the thesis once or twice a day will help you get writing again.

The Vanier application would not have to be submitted until fall and the weighting they put on the Vanier is different than the PGS/CGS scholarships. I am in an NSERC field but the criteria are the same. I applied for both NSERC PGS/CGS and the Vanier through separate applications this year. I found out first that I was awarded a NSERC PGS (21K per year) and didn't get a CGS (35K per year). About a week later, I found out I was awarded a Vanier CGS (50K per year). So, even though I was lower ranked in the academic based PGS/CGS competition, I was successful with the Vanier, a rounded, leadership-based scholarship. With the Vanier, academics (grades, etc.) do not matter as much as extracurricular and professional activities, contributions to your field (publications) and your ability to explain your research in laymens terms and apply it to real-world problems. So, if academics were a weaker part of your application and the other components were stronger, definitely apply to the Vanier. I would also say that if your chair wants you to apply, start now. It was a very stressful two weeks last fall trying to get everything done in time. I would say the complete application took one full week of my time to make sure it was perfect. Starting now will allow you to catch the small mistakes that are often missed when you are in a rush.