I've given this a lot of thought, and I think the best course of action is to experiment. The answer to this question is going to be different depending on how much power you have on the Steemit platform and what your inclinations are.
I'm inclined to always upvote my posts. I don't think it harms anything. I would say that, in general, you should do some upvoting for others before you upvote yourself. That's just my opinion.
In my experiments it doesn't effect whether people upvote you (or if it does, it's for the worse). People either like your content or don't.