Abandoning a depressed friend is the epitome of assholism. While you have the right to recognize your own limits, and you should, wording it the way you just did implies that you care more about how other people affect you than how you affect other people. If you have the strength of mind to realize that you have a problem, then you should have the strength of mind to sympathize and recognize when someone else is doing something out of emotion.
We all deal with anxiety and - sometimes depression - in differing amounts. TRUE depression is very different from "sadness" and "anxiety".
Acting as though you have no responsibility to help others because you have your own problems is fucking stupid.
Did you not notice that you come to this topic repeatedly to vent about your frustrations and failures? How would you feel if 99% of the people on this board just said "Well, fuck you. We have problems and the way you're behaving isn't nice, even if you have PTSD and are depressed".
Yea. I don't think you'd be feeling good. You'd be feeling rejected, which is the worst thing you can do with somebody who's depressed. You don't have to take their shit, but acting like a colossal fuckbag because you lack the fortitude to deal with it maturely does not make you the better party