I wouldn't delete a post based on a -1 personally. Maybe if you're at -5 and you find the answer is totally not helpful / even when you misunderstand a question and make an attempt to answer, hundreds of people will likely make the same error and having that up can help the site. It also can help someone with a similar problem but they find your answer.
Keep in mind - 4 down votes means that somewhere in the entire internet, 4 accounts at one point in time were cranky and didn't find that post helpful or clear or useful.
I'd focus on making new answers clear, relevant and think if you need to comment for clarification or post an answer that will be of use even if it's not what the OP wants to hear.
Lastly, there is the Stack Exchange Data Explorer where you can craft about any query you can think of to see posts by date, relative date, votes, etc...
It's not automated, but it's a system.