Don't take downvotes personally, or even as an indicator of whether your art is 'good' or not. Sometimes even the timing of when you upload an image (weekday or weekend, daytime or late at night, holidays, etc.) can have a HUGE effect upon how the voting goes.
Additionally, there are some groups of users who do nothing *but* downvote, because they can't be arsed to figure out how tag-blocking (filtering) works -- that or they're the type that enjoys spreading their self-loathing and misery to others. I've no way of gathering hard evidence of this, but I believe there to be at least a couple of bots out there that downvote images whenever one appears on the site with a tag they don't like. How sad a
sack of a human would one have to be, to write something like that? But if I've learned anything in the past two years, it's that there are more miserable, uneducated, foolish, self-assured assholes out there than anyone truly knows.
That said, art is purely subjective. All you can do is keep practicing, improving, and trying new things, and hope that people like the results. :)