Wow, reading what you wrote was like reading a perfect description of myself! Everyone I know knows that I read a lot and that I'm usually a pretty good person to ask for advice, especially regarding medical issues. However, I am the absolute worst following my own advice- it has really puzzled me for years as to why I am like this. It is very confusing, sometimes I feel like I don't follow my own advice because of the fact that I'm usually in a deep depression and deep down I really don't care what happens to me. I know that sounds terrible but I think that's what's happening, at least in my case.

Try an affirmation journal. You might be surprised what you can do when you've tasked yourself to do it. Just write down the things you want to see yourself doing, and go cross it out and write down more when you ready