Got notification I will have to claim PIP

Hi everyone, I have been a member for several years and looked in at the website now and again to try and keep up to date with things even though I wasn't going through any re-assessments. However I have just received notification that I will have to apply for PIP soon, and in my opinion I don't have a hope of getting it even though I currently get higher rate care and low rate mobility, judging by the self assessment. I get it for depression/anxiety and I have anxious/avoidant personality disorder, however my GP doesn't write letters as evidence anymore, I don't get professional help (I saw many psychologists, psychiatrists, CBTs years ago but none of then could 'cure' me). I take antidepressants (60mg fluoxetine) and there is side effects, but I don't see my GP about it anymore and my prescription is on repeat and never gets reviewed. I have a letter somewhere that is about 6 years old confirming my personality disorder. I would be grateful if anyone could give me any advice on how to try and get at least 8 points. I would also love to hear from anyone that has been successful with their claim for mental health. thanks in advance.

Thanks. Could you please direct me to the actual form they send out to you? And also, is it important to write a diary (I find it hard to concentrate), does it get submitted as evidence?