I think a cery good way to look at your own qualities is to look at your own core values. When you know what you really stand up for in life, then you'll see many qualities.
There're always qualities that you can be proud of there. After all, your core values have been guiding your life for such a long time.
If you still see nothing to be proud of there, then maybe it's time to do something about that. What about volunteering?