We can sometimes be our own worst critic of the things that we produce. I get this way about my art at times. I also used to constantly pick at my writing to the point where I didn't feel like posting anything. Perhaps that is why I only infrequently post. At least voting for myself occasionally has to a degree increased my fun factor around all of this.
It is difficult to know what benefit your votes are having. Posts that are well written provide value but other posts do too. There are so many levels of abilities and life situations that people are in and some intangible benefits for voting for content that others many not find first rate. If we all just voted for the very best, of the best, of the best, I don't think we would build much of a community. :D
I think you kind of have to follow your heart on some of this stuff and do what you feel is right.