When am I proudest of my writing? On days when it just is not going well. Today, I read through and worked on a a co-authored article; I am the second author. I really was not "feeling it," not inspired, and just was not doing great stuff. Yet, after an hour or so, I was able to get out 300 words. I will clear it up tomorrow, to assuage those feelings of "not good enough." I am working with a partner, after all.
But you know what? It are days like these that are the most important, the ones that in the long haul I feel most proud of. Not the days of awe-inspiring inspiration, but those when I am just grinding it out, doing my job. It is days like this that make, for me, the days of inspiration possible.
For me, the key is to not judge myself, but just do the work, the best I can, day after day, year after year. Of course, I need to evaluate the work, but this is different from judging myself, and comes after, not on, days like this.