INTJMom, what do you mean "beside yourself"?
Every type does have it's "defects" and it's benefits. I've always though of my self-criticism and my sensitive nature as just part of my personality, although at one point when I was very young I seriously thought something was wrong because I never saw it in other people.
You mentioned depression, inability to focus, self critism, softness (which I assume to mean sensitivity), and solitude. I think perhaps types are more inclined to some of these than others (perhaps depression is more likely with some kind of IXFP person, while coldness/lack of understanding could be more dominant in a XXTJ type, but that last one is pretty much a wild guess), but the really serious problems are also influenced by external experiences and/or biology.
I know that I personally experience those things more than most people by nature, because my external situation is really quite good, so it really only could be nature (and biology, I suppose) that causes my mood to be turbulent. I've always seen my inability to focus as a blessing in disguise, because it really has given me the ability to see the big picture of things and round it all up, and naturally explore a related topic (or, in laymans terms, my mind wanders off and I think about a new, although related, idea when the old one expires). The only problem with this "inability to focus" I have is that most things, such as school, are set up in a way that needs a different kind of attention. I've heard that people with ADD can "hyperfocus". I don't have ADD (to my knowledge), but I still have a hyperfocusing type thing going on, and it works well for me. Self criticism is the result of my perfectionistic ways, and my attitude that I can always grow and improve and learn. My self-criticism is very optimistic, in that sense, and even though I can be critical, I still like who I am. I feel that sensitivity is an important thing to have when learnign and understanding things, not a defect... softness is only a defect when it stops you from doing what you need to do, or when you can't control it appropriately.
As others have said, solitude is just a byproduct of introversion. I think a lot of those symptoms you mentioned are very much related in similar ways. For example, depression and self-criticism could really be the same problem manifesting itself in different ways. They are both negative, and are both similar in the sense that you feel down on yourself, victimized, and/or like a failure. Perfectionist tendancies could really just be a byproduct of being visionary or idealistic and needing to fill your vision of how something should be.