@TheStrugglingScientists I am not sure who advised this (Stephen King has a lot of useful advice on writing), but what worked always for me to overcome the procrastination/writer's block/however-you-call-it was to
1. set aside a consistent time every single day - say 2 hours of time
2. lock myself in the dept.'s library (or any other separate work room would do - not your office, nor home!)
3. disconnect from the Internet and phone, food and all other distractions
4. stare at the wall and see what happens

The idea is that writing is not only "writing", it's the whole context. And you need to spend time "writing". Whether you are really typing/scribbling/etc. is irrelevant, you can as well spend that time just staring at the wall, no problem, as far as that time is allocated to your thesis. My experience is clear: after a while of staring at the wall, you get so bored that writing the thesis actually feels like relief. So a bit by bit you start really writing. And once you start, it gets easier.

And also, one shouldn't strain themselves. 2 hours a day is just fine as far as you are consistent. Don't overdo, that would lead to this feeling of being invincible, which is exactly why we tend to leave important things for the last minute (because of the "hey, I've been there and done that" attitude).

Anyway, writing a book is difficult at first. And then it gets easier...

Good luck!.