The forgotten and ultimate survival tip for PhD

It's been a while since I've posted anything, and it is mostly due to me taking two months' leave from PhD. As such I have had literally nothing to comment on relating to my research. This post is in honour of someone who pointed out to me the key flaw in my "survival guide to PhD" post, that is, I didn't mention that a PhD student should never give up (although, life circumstance or job opportunity or any preferable change of direction in life are good reasons to quit). But for all of those out there with a general feeling of intellectual or motivational inadequacy, and are languishing over their PhD being a disaster and a dog's breakfast, you are not alone. Myself and so many others I know doing a PhD feel the same way. With the realisation that my PhD is likely to go for four years instead of three, I am currently coming to terms with a sense of failure, to myself and my supervisor, which is most likely unwarranted. I suspect it has a lot to do with high expectations for myself. This guilt and feeling of inadequacy and the fear of a sheer mountain of research and writing that has yet to be done, on top of a relationship breakdown and poor health, has literally caused me to breakdown. I've taken a break from PhD, but I won't give up. I know I shouldn't feel guilt at not being able to finish my PhD in three years, after all, if the government only wants to fund me for three years, that doesn't mean a PhD absolutely must be done in three years. Things take time, there's lots of waiting, and life happens. I've promised myself I'll get this PhD, and I'm going to do it. A close friend of mine has a great (and aptly Australian) definition for tenacity: "holding on for dear life, even when your dead", and I'll do my best to stick to that definition.
If you have a PhD story of dread or let-downs, feel free to share it in comments, after all, sharing the pain helps with the healing.